- The “stealth” Omicron sub-variant, BA.2, remains rare in the U.S., but experts warn cases could spike again if the variant becomes more prominent.
- Early research suggests that BA.2 may spread more easily, especially in unvaccinated people.
- The sub-variant highlights the importance of an Omicron-specific vaccine, experts say.
The discovery of a sub-variant of Omicron in the United States has prompted researchers to re-examine questions about vaccine efficacy.
The new strain, called BA.2, is a descendant of Omicron. It shares 32 mutations with the original Omicron variant, BA.1, but a few different mutations were detected in the spike protein.
Currently, BA.2 is still rare in the United States. However, experts worry that if the subvariant becomes more prominent, cases will spike again. According to experts, this may depend on the effect of BA.2 on vaccine protection and immune responses.
Pavitra Roychoudhury, M.S., Lecturer in the Department of Laboratory Medicine and Pathology at the University of Washington, said there are concerns that differences in BA.2 may render recent infections or booster immunizations ineffective.
“That means the tapering of cases we’re seeing now may not be sustainable,” Roychoudhury told VigorTip.
The data suggest that the original Omicron is better at evading vaccine protection or natural immunity from previous infection. A preliminary Danish study suggests that BA.2 is more transmissible than BA.1, but vaccinated and boosted people are less likely to transmit it to others.
Recent studies have also shown that mRNA enhancers can restore antibodies to protective levels against Omicron. While their protection against transmission of the virus varies, existing vaccines can still protect against severe COVID, regardless of the variant, Roychoudhury said.
While researchers continue to collect data, experts recommend that people continue to take precautions against COVID-19, such as wearing masks and maintaining social distancing.
Can mRNA boosters prevent Omicron?
Does BA.2 reduce vaccine effectiveness?
Researchers must evaluate laboratory studies and real-world data to determine the vaccine’s effectiveness against BA.2. That could take some time, Roychoudhury said, because there isn’t enough case data yet.
The original Omicron is easily detected in PCR tests due to the deletion of the S gene, also known as S gene target failure. But BA.2 doesn’t share the same characteristics, and it took researchers longer to identify the variant through genome sequencing. This resulted in BA.2 being marked as a “stealth sub-variant”.
However, according to Roychoudhury, the nickname is somewhat misleading.
“There’s nothing ‘hidden’. If you’re sequencing, you’re still going to find it,” she said. “It just tells us to be careful when interpreting spike gene target failure data, and to know that we should add a warning when we see a spike in target failure drop, which could mean Delta or possibly BA.2.”
Why doesn’t the US consider natural immunity?
Pfizer is continuing to develop an Omicron-specific vaccine, although it has not yet been approved by health authorities. The presence of BA.2 underscores the importance of these trials, Roychoudhury said.
“If there’s a vaccine that’s designed to be highly efficient for BA.1 or BA.2, and it’s very effective and can be used for a large portion of the population, then it has the potential to bring cases down to such low levels, maybe we don’t have to be too worried,” she said.
At the same time, researchers need to better understand the impact of BA.2 on infectivity and disease severity. “Ultimately, this is still a sub-lineage of Omicron, which we already know is extremely transmissible,” Roychoudhury said. “So, think it’s even more than that.”
what does this mean to you
Experts say we should assume that BA.2 is as transmissible as the original Omicron variant, if not more. Continue to implement COVID-19 safety measures, such as full vaccination and booster immunizations where eligible, wearing a mask in indoor public spaces, and getting tested if you are exposed to the virus.
The information in this article is current as of the date listed, which means that you may have updated information as you read this article. For the latest updates on COVID-19, visit our Coronavirus news page.
Correction – February 7, 2022: This article has been updated to clarify the effectiveness of existing vaccines against severe COVID.