Infection with the Omicron variant of the coronavirus can significantly improve the immune system’s ability to protect against other variants, but only in people who have been vaccinated, South African researchers have found.
In unvaccinated people, an Omicron infection provides only “limited” protection against reinfection, they reported on Friday in Nature.
In 39 patients who had Omicron infections – including 15 who had been immunized with vaccines from Pfizer/BioNTech or Johnson & Johnson – the researchers measured the ability of immune cells to neutralize not only Omicron but also earlier variants. At an average of 23 days after Omicron symptoms started, unvaccinated patients had 2.2-fold lower neutralization of the first version of the Omicron variant compared to vaccinated people, 4.8-fold lower neutralization of the second Omicron sublineage, 12-fold lower Delta neutralization, 9.6-fold lower Beta variant neutralization, and 17.9-fold lower neutralization of the original SARS-CoV-2 strain. The gap in immunity between unvaccinated and vaccinated individuals “is concerning,” the researchers said.
“Especially as immunity wanes, unvaccinated individuals post-Omicron infection are likely to have poor cross-protection against existing and possibly emerging SARS-CoV-2 variants,” they said. “The implication may be that Omicron infection alone is not sufficient for protection and vaccination should be administered even in areas with high prevalence of Omicron infection to protect against other variants.”
Different vaccines protect well against severe COVID-19
While the mRNA vaccines from Pfizer/BioNTech and Moderna generate higher antibody levels to protect against SARS-CoV-2 infection, AstraZeneca’s viral-vector-based vaccine provides equivalent protection against hospitalization and death from COVID-19, according a review of dozens of studies.
A panel of experts in Southeast Asia reviewed 79 previous studies for a study funded by AstraZeneca. Both types of vaccines showed over 90% efficacy against hospitalization and death, the panelists said in a report posted on Research Square ahead of peer review.
“The high level of antibodies formed after the COVID-19 vaccination is often interpreted as the effectiveness of a vaccine. We now understand that while initial antibody response levels can vary across vaccines, their ability to prevent being hospitalized or dying from COVID-19 is equivalent,” panel member Dr. Erlina Burhan, a lung disease specialist at the University of Indonesia, in a statement.
A spokesperson for the panelists said the findings suggest decision-makers should use any vaccine type that is accessible and optimal for their local situation, and that people who have a choice of vaccine should know that the one they can get quickest is best.
A separate study published in Nature Communications found that while Moderna’s mRNA shots provide slightly more protection against coronavirus infection than the Pfizer/BioNTech vaccine, “there are no differences in vaccine effectiveness for protection against hospitalization, ICU admission, or death/hospice transfer.”
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