May 1, 2022 - Health

Omicron subvariants can evade immunity from past infection, study says

A health worker administers a nasal swab test at a Testaro Covid-19 mobile testing site

A health worker administers a nasal swab test at a COVID-19 mobile testing site in Cape Town, South Africa, in December. Photo: Dwayne Senior/Bloomberg via Getty Images

Two new Omicron subvariants are able to evade antibodies from previous infections and vaccinations, according to a new South African study, Reuters reported.

Why it matters: The results of the study indicate that the two Omicron sublineages could results in a new wave of infections, the study noted.

Driving the news: The World Health Organization said last month that it was tracking cases of the two Omicron subvariants, BA.4 and BA.5, Reuters reported.

  • The BA.4 subvariant has been driving a recent spike in infections in South Africa, though hospitalizations have risen only slightly and deaths have remained stable, AP reported Friday.
  • Experts believe BA.4 may be more transmissible than the original Omicron variant or earlier subvariants, such as BA.2, per AP.

State of play: The study analyzed the blood samples of 39 people who'd been infected with the Omicron variant last year, 15 of whom were vaccinated and 24 of whom were not, per Reuters.

  • The study, led by the Africa Health Research Institute in South Africa, found that the blood samples of the vaccinated people showed a threefold drop in antibody production when tested against BA.4 and Ba.5, Bloomberg reported.
  • However, unvaccinated subjects who'd previously been infected with Omicron saw an eightfold drop in neutralizing antibody production when confronted with the new subvariants.
  • The study has not been peer-reviewed, per Bloomberg.

What they're saying: “The low absolute neutralization levels for BA.4 and BA.5, particularly in the unvaccinated group, are unlikely to protect well against symptomatic infection,” the study noted, per Bloomberg.

  • “This may indicate that, based on neutralization escape, BA.4 and BA.5 have potential to result in a new infection wave.”
  • "The vaccinated group showed about a 5-fold higher neutralisation capacity ... and should be better protected," it added, per Reuters.
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