• Health

Posts misrepresent CDC risk assessment of new SARS-CoV-2 variant BA.2.86; COVID-19 vaccines don’t increase the risk of infection

Posted on:  2023-09-04

Key takeaway

BA.2.86 is a new variant of SARS-CoV-2 derived from Omicron. It harbors a large number of mutations—around thirty—compared to Omicron. Preliminary results indicate that BA.2.86 is able to escape immunity, which means that the immunity built from vaccination or previous infection may not be very effective at protecting from BA.2.86.

Reviewed content


With the new BA.2.86 variant, “We’re in a situation where vaccination, according to the CDC, increases the likelihood of infection”

Source: YouTube, John Campbell, 2023-08-29

Verdict detail

Misrepresents source: In a risk assessment published in August 2023, the CDC expressed concerns that BA.2.86 may be more likely to infect vaccinated individuals compared to previous variants. This communication was misrepresented in social media posts, which inaccurately claimed the CDC said vaccination made it more likely for people to be infected by BA.2.86

Full Claim

the new BA.2.86 variant is “more contagious among vaccinated people than unvaccinated”; “We’re in a situation where vaccination, according to the CDC, increases the likelihood of infection”; COVID-19 vaccines “cause more infection”


The U.S. Centers for Disease Control and Prevention (CDC) published a document on 23 August 2023 summarizing what was known at the time about a new SARS-CoV-2 variant called BA.2.86. In the document, the CDC reported that “BA.2.86 may be more capable of causing infection in people who have previously had COVID-19 or who have received COVID-19 vaccines”.

This sentence prompted some people to claim the CDC had warned that the new variant was “more contagious among vaccinated people than unvaccinated”. In a video posted on 29 August 2023, YouTuber and retired nurse instructor John Campbell said “We’re in a situation where vaccination, according to the CDC, increases the likelihood of infection”. He added that the COVID-19 vaccines weren’t effective “because they cause more infection”. The video has received more than 980,000 views to date on YouTube.

Campbell has propagated misinformation on COVID-19 vaccines on multiple occasions.

However, these claims are unsupported and they misrepresented what the CDC said in its risk assessment document. What the CDC actually said is that previous infections or vaccination may be less protective against BA.2.86 than against other variants: “the large number of mutations in this variant raises concerns of greater escape from existing immunity from vaccines and previous infections compared with other recent variants” [emphasis added].

Therefore, the CDC didn’t say that COVID-19 vaccination increased the risk of infection by BA.2.86, contrary to what Campbell and others claimed.

BA.2.86 is a newly-detected descendant of the SARS-CoV-2 Omicron variant. So far, only nine cases have been identified across several countries. What has made scientists pay attention to this variant is that it carries 35 mutations compared to the Omicron variant XBB.1.5 that is currently circulating.

Changes in viral proteins due to mutations can reduce the protection provided by vaccination and previous infection. This is because our immune system, once stimulated by vaccination or infection, can detect and target specific patterns of virus proteins. If the virus mutates, the patterns in viral proteins that the immune system had learned to detect may no longer exist. This is called immune escape[1].

The original Omicron variant illustrates how mutation-based immune escape provides the virus an advantage. It harbored more than thirty mutations compared to the original SARS-CoV-2, many of which were in the spike protein[2]. Since most COVID-19 vaccines used the spike protein to train the immune system to detect the virus, changes in the spike protein of Omicron due to mutation reduced the ability of antibodies targeting the spike protein to recognize and target the virus[3].

A descendant of the original Omicron variant, itself already carrying numerous mutations, BA.2.86 has taken another leap forward, having developed about thirty additional mutations. These have also produced significant changes in the spike protein, leading the CDC to express concern in its risk assessment that immunity from vaccination or past infection may be further reduced relative to previous variants (immune escape).

Biochemist and assistant professor at Peking University Yunlong Cao shared preliminary experimental results on X/Twitter, which further support the CDC’s concerns over potential immune escape. Cao’s results showed that antibodies targeting SARS-CoV-2 that resulted from vaccination or past infection by other variants weren’t very effective at neutralizing BA.2.86. That said, these results were obtained through in vitro experiments and the actual degree of immune escape occurring in people remains to be seen.

In summary, social media posts misrepresented the CDC’s risk assessment of the BA.2.86 variant to claim that vaccination increased the risk of getting infected by this variant. This is false: the risk assessment had warned that immunity from vaccination or past infection may be less effective at protecting people from getting infected with the BA.2.86 variant, owing to significant mutations in the spike protein. In other words, BA.2.86 may be more capable of infecting vaccinated individuals compared to previous variants.


Science Feedback is a non-partisan, non-profit organization dedicated to science education. Our reviews are crowdsourced directly from a community of scientists with relevant expertise. We strive to explain whether and why information is or is not consistent with the science and to help readers know which news to trust.
Please get in touch if you have any comment or think there is an important claim or article that would need to be reviewed.

Published on:

Related Articles