People understandably crave a return to normalcy. However, some recent decisions by the American Centers for Disease Control (CDC) have the potential to worsen the pandemic.
Covid testing in the US has sharply declined since mid-April. This has led to scepticism about total case numbers and uncertainty about the proportion of the case downturn that is purely a function of reduced testing. Not only is keeping testing at a high level important for accurate case data, it is also vital to variant surveillance as variants of increasing infectiousness and concern have continued to form in recent months.
Even more troublingly, the CDC has recently announced that their officials will no longer track or investigate Covid-19 infections in vaccinated individuals, unless they have been hospitalized or died. But all cases are important. Asymptomatic cases of Covid-19 have led to such problems as glass opacities in the lungs and heart inflammation. It does not seem logical to exclude all but the most serious infections—unless the goal is simply to reassure the public.
Disturbingly, the CDC is also actively discouraging Covid testing for vaccinated individuals, even if they have been exposed to an infected person. The supposed relative lack of new cases in vaccinated individuals is therefore meaningless, given that we have not been testing most of those who have been vaccinated. Moreover, Covid vaccines are underperforming in individuals with immune system weaknesses or who are on immunosuppressive therapies, which may increase their vulnerability even when fully vaccinated.
The currently available vaccines do not prevent the virus from entering the body or produce sterilizing immunity. Vaccinated individuals are still susceptible to getting SARS-CoV-2 in their airways and could spread the virus, even if they are asymptomatic. A February 2021 article in the Journal of Otolaryngology notes:
Preclinical studies of adenovirus and mRNA candidate vaccines demonstrated persistent virus in nasal swabs despite preventing Covid-19. This suggests that systematically vaccinated patients, while asymptomatic, may still become infected and transmit live virus from the upper airway.
There is ongoing debate about the danger of viral spread from vaccinated individuals. Clinical Trials Arena has outlined two competing schools of thought:
- Vaccine efficacy numbers suggest that transmission from vaccinated individuals will not be an issue.
- We should measure the viral loads of those who are vaccinated but become infected and determine the actual risk of transmission.
Unfortunately, many public health officials contend that it is too onerous to collect data about transmission from vaccinated individuals. A Lancet article notes that vaccinated individuals “are probably less infectious than unvaccinated individuals are.” Probably—this is the level of certainty we are using to make vital public health decisions during a pandemic.
The CDC has decided to allow vaccinated individuals to stop wearing masks indoors, citing evidence of vaccine efficacy in lessening infections, but providing no evidence directly related to viral load or transmission—despite the existence of evidence that calls into question the prudence of mask removal guidelines. One study examined the relative viral loads of vaccinated and unvaccinated individuals infected with SARS-CoV-2. Viral loads were nearly identical for days 1–11 and a statistically significant difference was found on days 12–37: unvaccinated individuals had a mean infection cycle threshold (Ct) of approximately 25.1 and vaccinated individuals averaged around 26.9. (There is an inverse relationship between infectiousness and the Ct value: greater viral loads yield lower Ct values.)
Typically, Ct levels must be at or above 35 to be considered negative or undetectable: Ct values of 25–30 are considered moderately significant. While vaccinated individuals were slightly less infectious on days 12–37, it is not clear if this reduction is meaningful in terms of potential transmission. A Nature article notes “whether … observed reductions in viral load are sufficient to make someone less infectious in real life is not yet clear.”
Due to the CDC’s new guidelines, many professional sports organizations no longer require testing, quarantine (even after known exposure), masks or distancing for vaccinated athletes. Such policies imply a certainty that vaccinated individuals cannot contract and spread the virus in a form that could cause serious illness in themselves or others, which is inaccurate.
These decisions point to skewed priorities. There has been too much concern to reward the vaccinated and mitigate disappointment at having to continue health measures like masking. Moreover, the distinction between the effective immunity produced by the Covid vaccines and the sterilizing immunity produced by some older vaccines, such as those for smallpox and measles, is not well understood by the public. Public health officials either do not want to explain this distinction clearly for fear of discouraging people from getting vaccinated or feel that an explanation may not be clear to the public. So, instead of stressing the importance of continued indoor mask use, the CDC has caved to the outcries to allow more normalcy because, statistically, the overwhelming majority of vaccinated people will not die if they contract one of the current variants. This is a dangerous gamble.
We are closer than most people realize to a variant against which our existing vaccines will be ineffective. A May 2021 preprint study has compared the neutralizing titres produced by the Moderna and Pfizer vaccines against the original (wild type) virus strain and against the B.1.617.1 Kappa variant (one of the variants originally identified in India). The Moderna vaccine produced 1,332 titres against the wild type, but only 190 against the variant. The Pfizer vaccine produced 1,176 titres against the wild type and just 164 against the variant. An 86% reduction in total neutralizing titres was observed for both vaccines. Furthermore, a new Delta Plus variant (B.1.617.2.1) is evading treatments formerly used successfully with other variants and we do not yet know how much vaccine escape this variant may exhibit.
A future variant that escapes our current vaccines may form in a vaccinated individual. Variants can form when vaccinated individuals become infected (even asymptomatically) as the virus learns from being exposed to the vaccine in a process similar to the way in which bacteria can evolve resistance to antibiotics. Harvard epidemiologist Michael Mina notes that “you would see the most likely scenario for immune evasion and mutation that would improve the virus’s fitness against immunity—specifically in those people who have already been vaccinated or infected.”
Those who tout vaccines as the unilateral solution to the pandemic often point to Israel, where nearly 64% of the population have received at least one vaccine dose. They abandoned measures like masks and their case rate stayed quite low—until now. They have just announced that the Delta variant is causing a surge and around 50% of the cases are in vaccinated individuals. Indoor mask requirements are being reinstated and the Israeli Health Ministry has announced that vaccinated people who have been exposed will be required to quarantine for 14 days. The WHO has also announced that vaccinated individuals should continue to wear masks. WHO assistant director-general Mariangela Simao has commented, “People cannot feel safe just because they had the two doses. They still need to protect themselves … Vaccine alone won’t stop community transmission.”
Israel should be regarded as a bellwether for the rest of the world and indoor masking should be adopted. If a vaccine-escaping variant were to form in a vaccinated individual and this individual roamed maskless in indoor settings, the new variant could spread like wildfire and cause a massive increase in cases, hospitalizations and deaths. Given the current lack of testing among the vaccinated, such a variant would probably spread undetected until a hospitalization spike drew attention to the crisis.
Given all this, are we doomed to be sequestered, masked and distanced permanently? I hope not. But I believe the CDC’s decision to allow vaccinated individuals to go maskless indoors was premature. I think it is highly likely that the CDC will need to reverse course on this guidance sometime later this year, as the more virulent variants become an increasing problem. If they do, many individuals may refuse to comply. It is much easier to keep a requirement in place than to remove it and then reinstate it.
In the US, we are still far short of herd immunity. It is unclear how many people would need to be fully vaccinated to achieve that. Meanwhile, vaccination rates have tapered off markedly and polling suggests that a substantial percentage of people are unwilling to be vaccinated. If a vaccine-escaping variant forms and spreads before we achieve herd immunity, we could be back to square one.
So what measures should we take?
- Implement national regular testing programmes and contact tracing, supplemented by home testing kits, including for vaccinated individuals. Anyone who is infected, regardless of vaccination status, should isolate, even if asymptomatic. New Zealand has one of the lowest vaccination rates (around 11%) but has been extremely successful in controlling Covid-19 cases using such methods.
- Recommend that everyone wear N95 or equivalent masks indoors until transmission has been essentially stamped out. These masks are now more widely available to the general public. They are extremely effective at protecting both the wearer and others. Even if their use were not mandated, if a substantial number of people chose to wear them, that would be very helpful.
- Identify and use antiviral or anti-pathogen drugs that hamper or prevent SARS-CoV-2 from entering the cells in our bodies. It might be possible to use such drugs both for treatment and prevention. One possible example is the anti-influenza drug, Arbidol. Other antiviral medications are also being studied. A recent meta-analytic study indicates that Ivermectin could also be a promising treatment and prophylaxis.
- If possible, develop an improved vaccine that provides sterilizing immunity. While the current vaccines are highly efficacious at preventing serious illness, they do not keep the virus from entering the body, replicating in the airway, and being transmitted to others.
People are desperate for an end to the pandemic. But if we relax our vigilance prematurely, we may trigger escalations that prolong it indefinitely.