Will the Current Vaccines Protect Against Omicron Subvariant BA.2?

A subvariant of Omicron has been detected in the United States and it’s prompting researchers to revisit questions about vaccine efficacy.

Known as BA.2, the new strain 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.

For now, BA.2 is still rare in the U.S. However, experts are worried that cases will spike again if the subvariant becomes more prominent. According to experts, this may depend on BA.2’s impact on vaccine protection and immune response.

Pavitra Roychoudhury, PhD, MSc, instructor at the department of laboratory medicine and pathology at the University of Washington, said the fear is that the differences in BA.2 may render a recent infection or booster ineffective.

“That means that our gradual decline in cases that we’re seeing right now might not be sustained,” Roychoudhury told Verywell.

Data has shown that the original Omicron is more capable of evading vaccine protection or natural immunity from a prior infection. A preliminary study from Denmark suggested that BA.2 is more transmissible than BA.1, but people who are vaccinated and boosted are less likely to spread it to others.

Recent studies have also shown that mRNA boosters can restore antibodies to a protective level against Omicron. While their protection against virus transmission varies, existing vaccines still protect against severe COVID regardless of the variants, Roychoudhury said.

While researchers continue to gather data, experts advise people to keep taking COVID-19 precautions, such as masking and social distancing.

Will BA.2 Reduce Vaccine Effectiveness?

Researchers must evaluate both laboratory studies and real-world data to determine vaccine effectiveness against BA.2. This may take some time, Roychoudhury said, because there’s not enough case data as of now.

The original Omicron was easily detected on PCR tests through the absence of the S gene, also called S gene target failure. But BA.2 does not share the same feature and it takes researchers a little longer to identify the variant through genome sequencing. This has led to BA.2 being labeled as the “stealth subvariant.”

However, the nickname is somewhat misleading, according to Roychoudhury.

“There’s nothing ‘stealthy.’ If you’re sequencing, you’re still going to find it,” she said. “It just tells us to use care when interpreting spike gene target failure data, and knowing that we should add a caveat when we see the spike in target failure drop that it could mean Delta or it could mean BA.2.”

Pfizer is continuing to develop an Omicron-specific vaccine, although it has not been approved by health authorities. The presence of BA.2 highlights the importance of these trials, Roychoudhury said.

“If there is a vaccine that’s designed specifically with high efficacy against either BA.1 or BA.2, and it’s highly effective, and it can be given to a large proportion of the population, then it has the potential to get cases down to such a low level that maybe we don’t have to worry too much for a while,” she said.

In the meantime, researchers need to better understand BA.2’s impact on transmissibility and disease severity. “Ultimately, this is still a sublineage of Omicron, and we already know that Omicron is extremely transmissible,” Roychoudhury said. “So, think of this as being even more than that.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

Correction - February 7, 2022: This article was updated to clarify the effectiveness of existing vaccines against severe COVID.