The CDC is a confused organization. In early May, despite sound evidence that the authorized COVID vaccines effectively blunted SARS-COV-2 transmission, the agency insisted that fully immunized individuals continue masking up, despite fierce expert criticism. As I noted at the time:
Now that vaccine distribution is in full swing, some experts are criticizing the CDC for maintaining only slightly less restrictive guidelines for fully immunized individuals, because it signals to everyone else that the shots aren't very effective and could thus undermine further vaccine uptake.
The CDC updated its guidelines a little over a week later. Better late than never. But just days ago, the public health agency reversed its May guidance and recommended that fully vaccinated Americans wear masks indoors if they live in a region with “substantial or high rates of transmission,” arguing that the Delta variant is causing an alarming number of breakthrough infections. The media has been all too happy to run with the story, and we again face the prospect of elevated, unjustified vaccine hesitancy.
Considering the available evidence, which we'll do shortly, the CDC's new masking guidelines are baseless. The double-minded agency is catering to Americans with the lowest risk tolerance and undermining its messaging about vaccine safety and efficacy as a result.
COVID vaccines are still very effective
Sometimes government agencies have to make judgment calls based on incomplete information. Under those circumstances, they can be forgiven for making mistakes. However, that's not the case here. We know from multiple studies that the authorized shots are very effective against SARS-COV-2, including the dreaded variants of concern (VOC) like B.1.617.2 or Delta.
For example, here's the evidence for the Pfizer-BioNTech shot's efficacy against Delta. The graphic comes from a CDC presentation obtained by the Washington Post. The vaccine is relatively less effective against B.1.617.2. But when it comes to preventing hospitalization and death, the endpoints we're most concerned about, the vaccine still does a very good job. The authors of a study evaluating the Pfizer-BioNTech and AstraZeneca jabs, published in the New England Journal of Medicine, put it this way:
Overall, we found high levels of vaccine effectiveness against symptomatic disease with the delta variant after the receipt of two doses. These estimates were only modestly lower than the estimate of vaccine effectiveness against the alpha variant.
This isn't evidence that the vaccines are ineffective against Delta. Instead, as the authors explained, the study illustrates that “reduced effectiveness after the first dose would support efforts to maximize vaccine uptake [emphasis mine] with two doses among vulnerable groups in the context of circulation of the delta variant.”
Along the same lines, “In individuals that were not previously infected with SARS-CoV-2,” noted a July 9 article in Nature, “a single dose of either Pfizer or AstraZeneca vaccines barely induced neutralizing antibodies against variant Delta.” That's the bad news, but “a two-dose regimen generated high sero-neutralization levels against variants Alpha, Beta, and Delta, in subjects sampled at [Week 8] to [Week 16] post-vaccination. Neutralizing antibody levels are highly predictive of immune protection from symptomatic SARS-CoV-2 infection.”
If you're not yet picking up on the trend, consider the latest results from Pfizer's ongoing clinical trial evaluating the efficacy of its mRNA-based vaccine, which indicate the shot is having its intended effect. More than 46,000 people – 44,165 16 years or older and 2,264 12-15-year-olds – received two doses of the vaccine or a placebo 21 days apart. Results:
VE [vaccine efficacy] against COVID-19 was 91% through up to 6 months of follow-up, among evaluable participants and irrespective of previous SARS-CoV-2 infection. VE of 86%-100% was seen across countries and in populations with diverse characteristics of age, sex, race/ethnicity, and COVID-19 risk factors in participants without evidence of previous SARS-CoV-2 infection. VE against severe disease was 97%.
What about the vaccine's efficacy against variants?
Circulation of SARS-CoV-2 variants, some of which are associated with more rapid transmission, and potentially, greater pathogenicity, has raised concerns that such variants could evade vaccine-mediated protection. Our studies of in vitro neutralization of a variety of SARS-CoV-2 variants have, to date, found that all tested BNT162b2-immune sera neutralize all tested variants. [emphasis mine]
Vaccine expert Dr. Ben Locwin summed things up in an email to ACSH:
The current vaccines are spectacularly effective, and effective against VOCs, including Delta. Most of the severely ill and deaths from Delta are those who are unvaccinated.
That brings us back to our original point. The CDC's new masking guidelines all but guarantee the vaccine-hesitant will retreat into full-blown skepticism. “After you’ve been fully vaccinated,” the agency says, “you can resume activities that you did prior to the pandemic.” Oh, and by the way, “To maximize protection from the Delta variant and prevent possibly spreading it to others, wear a mask indoors in public if you are in an area of substantial or high transmission.”
As Dr. Josh Bloom argued here, the proposal is unworkable because high- and low-transmission areas may be separated by nothing more than a crosswalk. It's also possible that a county may move from low to high and vice versa before anybody who lives there realizes it's time to mask up. And if they're vaccinated, they may just not care. The bigger issue, though, is that the CDC's critics are eating this up.
For whatever reason, the pandemic seems to have robbed our public health officials of the ability to assess risk. Nobody denies that breakthrough infections are occurring (roughly 2 in 10,000 vaccinated individuals is the latest nationwide estimate), though it seems we're supposed to treat breakthrough COVID cases with an elevated level of concern. Locwin added in his email:
Even with very small numbers of breakthrough infections, what nobody else has pieced together yet in this story is the fact that our COVID-19 vaccines (now) are more effective than our typical flu shots on any given year (which tend toward 40%-60% effectiveness); and nobody mulls getting multiple flu shots as a booster sequence, nor masking out in public after flu vaccination.
The ultimate problem isn't Delta or any of the other Greek-letter variants. While they do pose a risk (particularly to the unvaccinated), they're no match for corporate media outlets addicted to fear-mongering and restive public health officials who can't stop sabotaging their own science outreach efforts. Winning the public's trust is hard; let's not make the task impossible by amplifying problems we've already solved.
Cameron English
Director of Bioscience
Cameron English is a writer, editor and co-host of the Science Facts and Fallacies Podcast. Before joining ACSH, he was managing editor at the Genetic Literacy Project.
