What we really know about the BA.5 virus variant and need for vaccine boosters

A new coronavirus variant called BA.5 seems to be a rallying cry for those who believe mutant viruses will reignite the COVID pandemic. Several “Influencers” have written stories with warnings about the potential severity of disease with this virus, and the likelihood it can infect individuals with prior immunity from vaccines or infections. 

The noise around this particular variant seems much greater than anything we’ve observed about COVID-19 in the past several months. It has even prompted an article in the Wall Street Journal suggesting caution about this virus. Others, such as Eric Topol, have taken to Twitter or Substack to tout unreviewed manuscripts showing the potential severity of this infection. 

Let me try to clarify what we really know about this virus.

  • First, like the other Omicron viruses, this virus can infect individuals with prior immunity to COVID-19, either from infections or vaccines. This BA.5 seems to have a greater ability to do this than prior Omicron viruses, and we have seen increases in the number of COVID infections since it arrived in the US in May 2022.
BA.5 arrived in the US in May and is now the dominant COVID virus (CDC).
  • BA.5 now accounts for 2/3 of COVID-19 in the U.S. The actual number of infections is not clear since many people are home testing and not reporting the infection. It also isn’t definitive how long BA.5 will take to speed through the population, but some South African data suggests the peak of infections is short lived.
South African data on COVID waves. BA5 is causing few deaths.
  • While the CDC indicates this variant is already dominant, the peak of infections may even have passed. Their data actually suggests a drop in COVID infections in the past few weeks.
CDC data seems to indicate COVID-19 cases are dropping over the past month. This is despite the presence of BA.5
  • The immune evasion properties of BA.5 do not seem to have added anything to clinical disease severity. Since the virus arrived in May we have not seen an increase in COVID with severe pneumonia needing oxygen, ventilator demand, or anything resembling last year’s COVID-19 severe infections.
  • Data isn’t available showing whether boosters with the current vaccines will protect against this or future Omicron variants. Most U.S. health authorities are not pushing a 4th booster for this virus, but are planning a fall booster campaign with vaccines updated to target Omicron subvariants, including BA.5.
  • Paxlovid and Evusheld treatments for COVID-19 still work well with BA.5. So don’t abandon their use for prophylaxis or treatment if you get infected.

In summary, lots of people have and will be infected with BA.5, but it is no reason to panic. Take appropriate mask precautions when in indoor spaces with lots of people, and treat yourself with Paxlovid if you have medical problems and become infected.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

4 thoughts on “What we really know about the BA.5 virus variant and need for vaccine boosters

  1. Dr Baker,

    Thank you for what you do with this series. I’ve been following it from from day 1 since I’m a MS in Molecular Biology from U of M.

    Question: would you wear a mask indoors? since I got COVID in April after returning to MI from a San Francisco trip not unlike your experience/timeframe in Washington DC. My experience was like that of bronchitis or flu and I took Paxlovid. Tested positive for 9 days with Antigen tests. I travel again in August and will mask up with KN95. Should I get another booster of the current vaccine? Before then? I’m skeptical that it will add protection in its current form. The Moderna ‘Omicron’ vaccine (early Omicron) won’t be ready until August, I‘ve heard and of course the BA 4/5 specific vaccine isn’t coming until Oct/Nov. How do we proceed except by masking up indoors in public? Until the late Fall?

    Thank you,

    Karen Karen L Roberts 415-999-6859



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