Your Guide to the Science Behind the CDC COVID-19 Recommendations
As we enter the third year of the COVID-19 pandemic, we’ve encountered multiple variants and resulting peaks. And as SARS-CoV-2 has evolved, so have the Centers for Disease Control and Prevention (CDC) guidances and recommendations by experts. Of course, there is not always a consensus between government health agencies and other scientists and doctors, and CDC advisories are no different[1,2,3]. When the new isolation time recommendation was announced, I had more friends and family want to discuss and understand the CDC guidelines and how they might have decided on the various recommendations. I have also seen many people online who are distrustful of the CDC when they see their contradicting information releases. While I’ve been keeping up with the new research, I haven’t taken a close look at the CDC press releases and their cited data. So, I endeavored to put the CDC advisories into context and do the research for those who were interested.
I’ve made two separate timelines, one for 2019–2020, and one for 2021. These are color coded as follows:
All of the information in the timeline images has been transcribed below in text format so that everything is searchable and reference links are in context.
Dates and events (left side of timeline) are bolded,
Event details (right side of timeline) have a vertical line next to them,
And my analyses of the CDC decisions are formatted in regular paragraphs. Here I did a deep dive into any sources that the CDC cited, and I did a literature search to see what data were available at the time of the CDC recommendation, as well as what new data have become available since then. The specific decisions that I analyzed are listed here:
2020 Mar 28・Jun 15・FDA issues emergency use authorization for hydroxychloroquine sulfate & chloroquine phosphate, then revokes said authorization after more data emerges.
2020 Oct 22・Differences in scientific opinion regarding remdesivir for COVID-19 treatment.
2021 Mar 8・CDC relaxes mask advisory for fully vaccinated individuals.
2021 Apr 2・CDC loosens COVID test recommendation for fully vaccinated domestic travelers.
2021 Apr 13・Apr 23・CDC and FDA paused and then continues use of J&J vaccine.
2021 July 27・Due to increase in transmission, the CDC advises everyone to resume indoor masking.
2021 Dec 27・CDC shortens recommended isolation and quarantine times.
2019–2020
Dec 31・World Health Organization (WHO) China announces first cases of pneumonia with unknown cause[4,5].
Jan 30–31・WHO and Health and Human Services (HHS) declare public health emergency[6,7].
Mar 11・WHO declares COVID-19 pandemic[8].
Mar 15・US begins to shut down[9].
Mar 17・First mRNA-1273 Moderna Vaccine human trials start[10].
Messenger RNA (mRNA) vaccines have been in the works for decades[11,12,13]. One of the main pioneers of mRNA vaccines is Katalin Karikó, PhD, who is currently the senior vice president of BioNTech[11]. Human trials started almost immediately after COVID-19 was declared a pandemic[10,14], and sources estimate that between $18–39.5 billion was supplied by the US government to fund the concurrent processes that developed safe and efficacious vaccines[15].
Mar 28・Social distancing measures are announced
Previous influenza outbreaks were combated with social distancing, producing significantly lower infection rates[16,17]. As SARS-CoV-2 is also a respiratory virus, a similar non-pharmaceutical response was implemented.
Mar 28・Food and Drug Administration (FDA) issues emergency authorization for hydroxychloroquine sulfate and chloroquine phosphate. CDC warns against use of chloroquine phosphate to prevent COVID-19 without medical input.
As cases rise exponentially, FDA grants emergency use authorization (EUA) for hydroxychloroquine sulfate and chloroquine phosphate products based on the data by Gautret et al. that treated patients had reduced viral load significantly earlier than patients who were untreated[18]. The CDC simultaneously advises the public not to self medicate with chloroquine aquarium chemicals[19]. After further research, the FDA revokes the EUA when multiple studies show no significant effects[20,21,22,23,24].
As the pandemic ramped up, there was an organized effort to combat the SARS-CoV-2 virus with pharmaceutical measures, which included both prophylactic and therapeutic treatments[10,18]. However, scientists understood that these treatments would take time, so we implemented scientifically backed non pharmaceutical interventions (NPIs) like social distancing and mask mandates to battle transmission[16,17,25,26]. These measures have been backed up by further research since 2020[27,28,29]. The EUA that was first granted and then rescinded for hydroxychloroquine sulfate and chloroquine phosphate products reflects the continual scientific process. While early data supported its use, new studies found that COVID-19 patients did not significantly benefit from its administration[20,21,22,23]. Actions like this are a reflection that the scientific and medical systems are working.
Apr 3・CDC announces mask wearing guidance.
After numerous studies showed that wearing masks reduced COVID-19 transmission[25,30], the CDC advises people wear masks when outside the home. Further data support these initial findings[26,29].
May 1・FDA issues EUA for remdesivir antiviral drug.
May 28・US death toll passes 100k.
Jun 15・FDA revokes EUA for hydroxychloroquine sulfate and chloroquine phosphate.
Sep 22・US death toll passes 200k.
Oct 22・FDA approves remdesivir for COVID-19 treatment.
Remdesivir was found to be efficacious in preliminary studies[31,32]. Follow up studies show sufficient data for FDA approval and for NIH to recommend use of remdesivir for COVID-19 cases[33,34]. However, WHO puts out a statement that there is not enough evidence to support its use[35,36,37,38].
The discrepancy between the stances of FDA and WHO regarding remdesivir reflect the difference in necessary data for approval and functioning of health agencies in different parts of the world. While the FDA controls the available therapies for the United States, WHO’s suggestions do not actually impact medicines available to the public. Other countries and governing health agencies have allowed the use of remdesivir in some capacity: The European Union, Japan, South Korea, The United Kingdom, Taiwan, India, Singapore, Israel, and Australia[39,40,41]. Within the study of COVID-19, and for all fields of science, researchers don’t always agree. In this case, the FDA reviewed the data and decided that the data showing remdesivir helps COVID-19 patients was sufficient for use through the FDA’s Coronavirus Treatment Acceleration Program[42]. This does not, however, mean that corners were cut scientifically[43]. Similar to vaccine development, a lot of money and resources were thrown at research, development, and clinical trials. As more research comes out about remdesivir and other COVID-19 therapies, any of these decisions are liable to change. I can only speculate how the WHO and other health agencies used the same data and came to different conclusions. It is possible that the WHO international guideline development group has different standards for significant improvement. The WHO statement acknowledged need for more data, but hasn’t been updated since the end of 2020[35].
Dec 11・FDA issues EUA for BNT162b2 Pfizer-BioNTech COVID-19 vaccination.
Sufficient data showed that the BNT162b2 Pfizer-BioNTech vaccine was safe and elicits immune response[44,45,46]. Further studies contributed to the decision for the FDA to approve the vaccine for those 16 and up[47]. More data informed the expansion of the FDA EUA for younger age groups and for use as a booster[48,49,50,51].
Dec 14・First American receives COVID-19 vaccine.
Dec 14・US death toll passes 300k.
Dec 18・FDA issues EUA for mRNA-1273 Moderna COVID-19 vaccination.
The mRNA-1273 Moderna vaccine was first made available under EUA for those above 18, as data found the vaccine to be safe and efficacious[52,53]. The FDA EUA has been expanded with further data to include younger age groups and a booster vaccination[54,55,56].
Dec 30・Alpha variant confirmed in the US.
2021
Jan 18・US death toll passes 400k.
Jan 25・Gamma variant confirmed in the US.
Jan 28・Beta variant confirmed in the US.
Feb 21・US death toll passes 500k.
Feb 27・FDA issues EUA for Ad26.COV2.S Johnson & Johnson (J&J) COVID-19 vaccination.
The Ad26.COV2.S J&J adenoviral vector vaccine was given EUA by the FDA based on clinical trials showing that the vaccine was safe and effective[57,58,59]. Concerns about blood clots later caused the FDA and CDC to first rescind and then reinstate the J&J vaccine recommendation in April[60,61,62]. The EUA has now been expanded to include a booster J&J vaccine[63].
Mar 8・CDC advises that fully vaccinated individuals can gather indoors without masks.
The CDC determined that benefits for interacting without masks outweighs the potential risks of transmission for fully vaccinated individuals[64,65,66].
I will admit that I was surprised that this recommendation was based solely on a modeling paper that has yet to be published[64]. Other data cited by the CDC science brief find that NPIs will still play a role in mitigating transmission even as vaccines roll out, and we are warned that relaxing measures too early will result in no case reductions[66]. The paper that modeled vaccine implementation and reduction of NPIs showed that a rapid and early adoption is key to reducing COVID cases and allow for relaxed mask usage. It seems the key here is that the CDC was relying on the rapid increase in vaccinations. At this point, 16.3% of the US had received at least one dose of an mRNA vaccine and considering the increasing trend, the CDC banked on a continual increase in vaccinations[67]. The CDC also had to contend with NPI adherence and public moral. At this point, the US was about one year into the pandemic, and vaccines provided a light at the end of the tunnel that we could look forward to. The CDC also cited a study that found people would be less likely to vaccinate if they would still have to wear masks[68]. And according to a survey, people were already starting to return back to their lives regardless of guidelines[69]. The advisory to allow fully vaccinated individuals to gather without masks provides an incentive for those who would otherwise remain unvaccinated. It provided a morale boost as we hoped for the end of the pandemic (oh, my sweet summer child). It seemed this was less about the epidemiological science and more about public health as a whole, including mental health and adherence.
Mar 19・CDC recommends that school children can reduce social distancing to 3 feet with indoor masking.
There have been growing concerns that students are falling behind in their schooling due to the pandemic[70]. As in person learning continues, the CDC reduced social distancing to 3 feet after a study showed similar transmission for ≥3 or ≥6 feet distancing[71,72].
Apr 2・CDC announces that fully vaccinated people can travel safely domestically without COVID test.
As more adults are getting vaccinated, the CDC cites the vaccines’ preliminary efficacy data and their own modeling for their guidance that fully vaccinated individuals do not need to get tested before traveling domestically[73,74,75,76].
This travel advisory CDC Newsroom Release was not only based upon preliminary vaccine efficacy data. They also cited a science brief that I was able to access with the internet archive Wayback Machine[77]. This science brief actually focused more upon the assumed risks of travel and the use of NPIs. The CDC opened their travel advisory with a background stating that there is inherent risk of transmission when traveling. They also state that “to reduce this risk, CDC has recommended that all travelers be tested for the virus 1–3 days before departure, […] combined with a second test 3–5 days after travel and staying home to self-quarantine for a full 7 days after travel if the post-travel test result is negative. If post-travel testing is not done, the recommendation is to extend self-quarantine to 10 days after travel.” I have omitted their line that a test or previous infection is required for international travel. This was added on April 2, 2021. The previous iteration of this website was updated on March 8th when fully vaccinated individuals were allowed to gather indoors without masks. The language used here does not reflect their final recommendation to allow domestic travel without testing.
The CDC also did their own modeling and calculations using the most up to date vaccine efficacy data at the time combined with modeling by Johansson et. al. to determine the need for NPIs with vaccinations. The Johansson et. al. model calculated the effectiveness of pre travel isolation, pre travel testing, post travel testing, and post travel quarantine without the use of vaccines[78]. The CDC’s model found that pre travel self-isolation, pre travel testing, and post travel testing, did little more to reduce transmission rate if we assume that the vaccine is 90% effective. However, if these NPI measures are used by unvaccinated individuals, they are more than 30% more effective compared to travelers who did not take NPIs and had a 60% effective vaccine. When considering the risk of transmission at origin and destination, the model showed that the greater number of individuals that are vaccinated at either location, the lower the transmission.
The CDC specifically pulled these numbers in reference to the above model, with combined vaccine efficacy (VE) to mean the percentage of susceptibility and transmission if infected:
Now it must be stated that the COVID Data Tracker Weekly Review that was also updated on April 2nd stated that 56.1 million people were fully vaccinated[79]. This is 16.9% of the total US population. Keep in mind that at this point younger age groups were not eligible for vaccination, so percentage of eligible population is approximately 10% higher. At this time, 99.6 million people, or 30% of the population had one dose.
Anecdotally, I was trying to get a vaccine as soon as possible, as someone who was not technically in any of the high risk categories even though I had been back at work for many months. At around this time I was struggling to get a slot to get vaccinated in my county, and lines were out the door at vaccination locations. Even elderly people were made to wait in lines that stretched for at least a quarter of a mile (yes, I went and measured on google maps) and wrapped around an entire building complex. Getting vaccinations was very difficult at the beginning, and very few people were fully vaccinated at the time of this report.
If the general population was on average below 20% vaccinated, why were the numbers pulled from this model 0%, 50%, and100%? I don’t have access to the actual data, but by eye (red rectangles) it seems that if no NPIs were used with an origin and destination population that was generously 20% vaccinated, the risk reduction would be anywhere from 20–30% depending on if the vaccine was 60% or 90% effective. Of course, vaccination rates were increasing steadily, but it would take until April 22nd for the US to reach 1/3 of the 18+ population to be fully vaccinated[80]. At this point, the vaccination rate had peaked, and we wouldn’t reach 50% of the total US population fully vaccinated until August 13, 2021[81].
With the known data and hindsight, it seems that the CDC was very optimistic with the increasing number of vaccinations in early April. We must also consider the burden of testing on our resources. By April of 2021, more than 60% of the usual traffic was going through airports compared to 2019 numbers[82]. More and more people were flying as we came down from the winter peak, and we were more optimistic. Flying was going to increase, and recommendation of testing of vaccinated people did not look like a wise use of resources, especially with fairly efficacious vaccines for the original and the current variants.
Due to this optimism, Abbott soon closed an at home COVID test manufacturing facility that would have great impact further down the line as the Omicron variant surged and tests became very difficult to come by. The guidelines provided by the CDC in the 2021–2022 winter would reflect this.
Apr 13・CDC and FDA recommend pause of J&J vaccine due to blood clot concerns.
Apr 23・CDC and FDA recommend continuation of J&J vaccine for those 18 and older.
After 6 cases of blood clots in individuals who received the J&J vaccine, the CDC and FDA recommended a pause in J&J vaccinations so that further data analysis could be considered while ensuring public safety during this interim[60]. After considering all available data in their safety review, both the CDC and FDA reinstated their recommendation for use of the J&J vaccine[61].
In the case of the J&J vaccine, the decision to do a safety review seemed to have a dual purpose of both double checking the data and also to reassure the public. It was found that after the vaccine was paused and reinstated, the public trust in vaccines overall increased[83]. Unfortunately, this came at a cost of reduced trust in the J&J vaccine[83,84]. If we are to consider the data on the J&J vaccine by itself, the cases of thrombosis and thrombocytopenia are low[85]. The potential risk compared to known benefits are quite stark, as COVID-19 has also been shown to cause blood clots. COVID patients have almost a 9-fold greater chance of getting a pulmonary embolism compared to healthy patients[86]. However, as more studies have come out since April 2021, data show that it is less effective compared to the mRNA vaccines available, so the CDC no longer suggests the J&J vaccine as a possible first choice. Boosters are suggested to be either Pfizer-BioNTech or Moderna after only two months since getting the J&J vaccine[85]. The CDC cites both the reduced efficacy and the known link between this vaccine and thrombocytopenia syndrome (TTS) as reasons to suggest the mRNA vaccines before the J&J[85]. So far, 18 million doses of the J&J vaccine have been administered, with 57 cases of TTS, and 9 deaths[87]. So, while chances of TTS are very rare, and the symptoms of COVID-19 can be much more severe (and having a vaccine is overall better than none) the data support that this vaccine is no longer a top suggestion.
Jun 1・Delta becomes dominant variant in the US and causes 3rd wave of cases.
July 27・Due to increase in transmission, the CDC advises everyone to resume indoor masking.
Due to an increase in cases as the delta variant spreads, the CDC reversed its mask guidance from April of this year[88].
As the SARS-CoV-2 virus mutates, more variants of concern became more prevalent. This announcement came as the delta variant became the dominant variant in the US, kicking off a summer surge that took place during the supposed off season. Early data showed that the delta variant had higher viral load than previous iterations, suggesting that delta would be more transmissible[89,90]. More breakthrough infections occurred with delta, even though vaccinated individuals still had less of a chance to suffer from severe disease[91,92]. Since we know that masks have solid scientific backing, it makes sense for the CDC to recommend relying more on NPIs as cases rise and more data comes out.
Aug 6・CDC study shows that those who previously contracted COVID-19 were half as likely to get reinfected if they were immunized vs not.
A Morbidity and Mortality Weekly Report published a case study of individuals in Kentucky, in which a cohort of previously infected and vaccinated individuals were compared to those who were previously infected and unvaccinated[93]. The unvaccinated people were 2.34 times more likely to become reinfected, which highlights the importance of vaccine protection.
Aug 23・FDA approves BNT162b2 Pfizer-BioNTech COVID-19 vaccine.
The FDA reviewed further data that lead to the approval for the BNT162b2 Pfizer-BioNTech COVID-19 vaccine that showed safety and efficacy[47]. The mRNA-1273 Moderna vaccine was submitted for approval around the time the BNT162b2 was approved and is still in review[94].
Oct 21・CDC endorses Advisory Committee on Immunization Practices (ACIP) recommendation for those who are at high risk to get a booster shot.
Data showed that there is waning immunity a few months after someone is fully vaccinated[95,96]. The emerging evidence that supported boosters or high risk individuals was posted on the CDC booster information website[97,98]. The booster recommendation was then expanded to anyone over 18 years old one month later[99].
Oct 29・CDC study shows that vaccination produces more protection than a previous infection.
A study of COVID-19 cases across nine states reported that those with a previous infection and no vaccine were 5.49 times more likely to contract COVID-19 compared to those who had been vaccinated at least three months prior[100].
Nov 26・Omicron variant reported to be new variant of concern.
Nov 29・CDC recommends everyone over 18 gets boosted after 6 months since full vaccination.
Dec 13・ US death toll passes 800k.
Dec 27・CDC shortens recommended isolation and quarantine times.
The omicron variant was first reported to the WHO on November 24[101]. It was soon identified as a variant of concern[101,102,103]. Since then, more data has come out about the variant, informing the new measures released by the CDC[104,105]. It has since produced the greatest daily cases peak since the start of the pandemic[106,107]. However, daily deaths have not surpassed the 2020–2021 winter peak[106,108].
The new shortened isolation times and recommendation not to test before resuming normal activities has made many people uneasy, and has caused healthcare workers and other essential workers to be worried for their safety[109]. In conversations I’ve had with friends who are healthcare workers, frontline workers, scientists, students, etc., many doubt the science behind the advisory. The guidance seems to have come right after thousands of flights were canceled or delayed due to COVID concerns during the holiday travel surge and as hospitals were slammed with new COVID patients[110,111]. The timing has left many wondering whether the CDC guidance sacrifices essential workers to treat COVID patients and ensure the economy continues to run.
Data compiled by the WHO about previous variants noted that the original SARS-CoV-2 and earlier variants had longer incubation times and infection periods compared to the reduced timeline of both delta and omicron[89,112,113]. Most of the data I was able to find only discusses the incubation time (time from infection to when symptoms appear). However, the time in which someone can infect others extends into and past the incubation period. Overall, incubation times were cited to be more than 5 days for the original and early variants, 4 days for delta, and 3 days for omicron according to a 6 person case study MMWR from November[113]. The CDC estimated that infected people are most contagious between two days before symptoms starts and three days after symptoms start for omicron, but did not cite their source[114]. Assuming this is correct and with data known when this advisory was released, this infectious period is likely similar, maybe longer for previous variants due to their elongated disease progression timeline.
With the delta variant, it was found that much of the spread was due to pre-symptomatic or asymptomatic spread[118]. This type of spread remains an issue with new variants, especially as our vaccines are found to be less effective at reducing infection[119]. It must be noted that vaccines, especially boosters, are still very effective at reducing severe disease[120,121]. So, the CDC guidelines that asymptomatic individuals or symptomatic individuals with resolving symptoms isolate for 5 days post positive test or start of symptoms, falls within the 6 person omicron case study[113,114]. If someone were to test positive on the first day of virus shedding, the subsequent five days should encapsulate the most contagious time of their infection. It is likely that people will actually realize they have COVID part way through the most infectious period, in which case the 5 days should even provide a little buffer for the suggested omicron timeline. During that time, the problem would be asymptomatic and pre-symptomatic transmission. However, this 5 day most contagious range might not be the case for the delta variant and does not encapsulate the entire infectious period.
The shortened recommend isolation time was announced around the same time that the CDC revised their previous US variant calculations. On the 28th, the CDC announced that their calculations that omicron made up 73% of US COVID cases was incorrect, rather omicron only made up 59% of known cases[122,123]. What’s odd is that the official CDC variant proportions website still says 73%, and I can’t find an official announcement or news release regarding the data revision. Every news site I’ve found links to the variant proportion data tracker site (which doesn’t load in properly in the Wayback Machine since they pull data from a third party). Some quote an unnamed CDC spokesperson who noted that revisions are expected as better data is found, and that omicron is still growing steadily. I was able to find a screenshot of the revised CDC data on Twitter, which was retweeted by former FDA commissioner Scott Gottlieb. He said that the data suggests that much of the hospitalizations may be driven by delta[124]. During the time in which delta was the more prevalent variant, Davies et. al. published that 13% of COVID patients still maintained enough viral load to transmit after 10 days[125]. Given this information, this means that 41% of the cases were delta or “other” and transmission was still occurring after 5 days. Even though omicron was without a doubt increasing, asking the many people who were likely infected with delta to reduce their isolation time and not test before returning to their daily activities was not handled properly. Of course, this is all said with hindsight.
The science brief for reducing quarantine time was last updated on December 2nd, 2020[115]. I’m surprised that this page is more than a year old given the lack of citations/data and how much attention has been garnered by the recent quarantine reduction. This brief supported reducing the self-isolation time to 10 days without symptoms or testing, or 7 days with a negative COVID test exiting quarantine[115]. This was supported by a few published and preprint (not yet peer reviewed) papers. Wells et al. modeled and then applied their model to a real-world situation, showing that testing to end quarantine could reduce isolation times to 7 days, whereas relying on only pre-isolation testing could not consistently reduce transmission, and therefore should not be used to impact isolation time[116]. Other data cited similarly supported the need for post-isolation testing for a safe quarantine reduction[115,117].
This science brief also has a section on additional considerations, which highlights the need for COVID testing resources for the suggested quarantine reductions. They also mention the need for equitable access to these resources[115]. Unfortunately, the US is very behind on COVID testing resources, and the recent White House rapid test mail distribution is far from equitable. Those who do not live in housing that has been properly registered have been denied tests (multiple unit housing, non-residential, dorms…). Those who are homeless cannot input an address into the form and receive their tests. Those who live with more people are still restricted to 4 tests per household. Those who are immunocompromised and therefore more susceptible to COVID infection are similarly unable to receive more tests. Those who are in the high-risk category for other reasons (healthcare workers, front line workers, long term residents…) are also severely limited by the distribution system. If we are to follow the data reported by the CDC, the lack of COVID testing is extremely detrimental to safely reducing quarantine times.
We must also look at the data that do not support the 5 day isolation time. A modeling study by the UK Health Security Agency found that 5 days after symptom onset or a positive test, 31% of people would remain infectious[126,127]. This then drops to 1% after 14 days. With almost one third of individuals still infectious after 5 days, it would not be advisable to maintain this self isolation guidance. A study by Japan’s National Institute of Infectious Diseases and the Disease Control and Prevention Center within the National Center for Global Health and Medicine determined that patients still had viral RNA at 3–6 days after diagnosis or symptom onset for the omicron variant[128]. From 7–9 days, patients still consistently tested positive for viral RNA. The UK Department of Health and Social care released a notice earlier in January that those who tested positive may reduce their isolation after 5 days as long as they receive two negative lateral flow tests on two consecutive days[129]. While they did not cite any of their data, the press release states that ending isolation after day 5 with two consecutive negative tests versus no testing reduces the percentage of infectious individuals from 20–30% to 7%[129]. Much of these data did not differentiate between symptomatic or asymptomatic cases, but the study out of Japan found that from 6–9 days, 75% of asymptomatic patient samples tested positive for viral RNA through polymerase chain reaction (PCR)[128].
There has recently been another study released in preprint regarding the omicron disease progression timeline. Hay et. al. completed data analysis on PCR testing from the National Basketball Association (NBA) health program[130]. They used PCR cycle threshold (Ct) of < 30 to determine which samples had greater viral load. To run PCR, the genetic material is amplified by cycles so that the virus can be detected in the sample. Lower Cts mean that fewer cycles were needed to detect the virus, which means the patient is more transmissible. At 5 days post positive test for omicron (≤ 1 day between negative and positive tests), 52% were still positive with Ct < 30[130]. This dropped to 25% on day 6, and 13% on day 7. Overall, the omicron variant had an infection duration of 9.87 days. When compared to their previous work looking at the delta variant, Cts were slightly higher (lower viral load) and the duration was one day fewer. For omicron, the peak occurred after 4.52 days, which falls within the 5 day isolation time. However, as viral clearance begins, there is still ample viral load that would allow for transmission beyond the quarantine time.
Now that we have considered the scientific evidence and data regarding the suggested reduction in self-isolation, I found the arguments for this recommendation to be on very shaky foundations. We have had multiple changes in guidance throughout this pandemic, including mask guidelines and treatment recommendations. With more and more data coming out about omicron, it would make sense to increase the isolation timeline. The fact that the CDC has consistently been open to changing recommendations as we learn more is evidence that science is working as it should. Changing the isolation recommendations now would reflect their trust in science. However, at this time positive cases look to be peaking in parts of the country, and reducing the isolation time might not greatly affect case numbers. Unfortunately, deaths are likely to continue rising[131]. It would be difficult to determine how changing isolation recommendations would impact these deaths.
It must be noted that the CDC does not only concern itself with available scientific data. It’s a government entity that must take the economy and resources into account. Our healthcare infrastructure was (and still is) ill equipped for a pandemic and cannot provide everything that is needed in this situation[132]. One way the CDC is attempting to remedy pandemic preparedness is by creating the Center for Forecasting & Outbreak Analysis, which will hopefully make us better prepared in the future[133]. Right now, testing manufacturing is far behind what is needed[134]. The US is also contending with a volatile market and workers who are getting sick at much higher rates than with previous variants[135,136]. Workers who are isolating cannot contribute to the functioning of our society. It seems that the CDC has made the decision to compromise an increase in infection rates from post-isolation transmission for a larger work force and reduced pressure on our COVID resource infrastructure. Honestly, making these decisions is not an enviable job. Having to juggle the public health implications with the pressures from the rest of American livelihood sounds, frankly, awful. I haven’t even dug very deep into the mental health implications of prolonged isolation and compliance with public health guidelines, which the CDC had to take into consideration. Overall, I don’t agree with this specific recommendation from a scientific and medical standpoint, but I can’t say I’d make a different decision with the same pressures and information available to those in this position. However, as we surpass 900,000 COVID-19 deaths in the US, I worry that the cost is just too high. The amount of pressure that we put onto those propping up our society has made many people burnout and/or quit[137,138,139,140]. Our support system is dwindling, and it is unfair to assume that frontline workers should put their lives on the line in more capacity than we’ve already asked of them.
Digging through the CDC website, I was surprised by how little they actually cite their data or studies. Maybe CDC Newsroom press releases aren’t meant to be a source for scientific discussion, but even when they mention specific data, they often don’t link or cite the study[72,114,141]. These press releases were also some of the only available resources for information on new recommendations that were not updated and erased. Understanding the new guidances were also difficult in context, as many of their website pages were updated so that we could not see what was added or removed. While this would make things streamlined for those looking for current information, it does contribute to confusion when the public has seen what seems to be conflicting information because new data has emerged.
Overall, the CDC recommendations align with the known data at the time. They sometimes extrapolate from what is currently known through modeling and similar practices, which is very common in the scientific community. The conclusions that they come to with input from these models look to be very optimistic about the future. Much of the loosening of restrictions come during late spring/early summer after vaccines were being pushed out to the general public. While I do think we all had hope that the vaccines would greatly ease the burden of COVID-19, the CDC assumed that this would be the case and made recommendations on these assumptions. Unfortunately, vaccinations were too low to make a dent in our NPIs in the long run, especially as new variants evolved. Please note that vaccines with boosters are still the best way to reduce the risk of severe disease, protecting you, those around you, and our healthcare workers[120,121].
Additionally, it looks like some guidelines have been influenced by other factors in our society, such as economic, resource, or adherence factors. These are very important to a functioning society, but the reduced isolation time with a crippled COVID testing infrastructure put a preponderance of the pressure onto our healthcare workers, teachers, and other frontline workers who have been bearing the brunt of this pandemic for more than two years now. CDC decisions also explicitly stated that certain measures were suggested because of mental health and exhaustion from NPIs. Anyone will get burnt out with reduced social interactions and strict restrictions for an extended period of time, so it was important for the CDC to recognize that. An example of this understanding was when the CDC recommended that fully vaccinated individuals could gather indoor without masks[64, 65,66]. There was preliminary data that the vaccines would be protective, and polls showed there was greater incentive to get the vaccine if people could resume some of their regular activities without masks[68]. The CDC can put out all the recommendations it wants, but it won’t matter if people don’t actually follow the guidelines.
Public health during a pandemic is a very messy science. Unfortunately we cannot only rely on hard data with all of these confounding factors. I’m sure that guidelines from governing health agencies were released with the utmost care and consideration in these circumstances, even if I don’t agree with all of them. Hopefully taking a look at the science behind these calls and the other aspects that influenced them will help in your understanding of our response to COVID-19.
Keep in mind that because the CDC updates its websites, CDC sources are liable to change, and it might be necessary to access them through the Wayback Machine in the future.
Side note, all of you news outlets with your COVID news behind a paywall: Shame on you. Even scientific journals are making COVID articles free for the public and we all know how much they love to gate keep.
