Omicron subvariant BA.2 is replacing its sister version, BA.1 is the predominant form of SARS-CoV-2 in many countries, leading scientists to wonder if the COVID-19 pandemic will once again throw these regions into chaos. But a study published March 13 found that mRNA vaccine Provided similar degrees of protection against both strains—although protection against SARS-CoV-2 infection and symptomatic disease waned within months of the third dose.
The study, published on the preprint server medRxiv, has not yet been peer-reviewed.
BA.1 subvariants have been known to researchers for months evade most protections mRNA vaccines protect against mild to moderate disease. Scientists quickly realized that BA.2 spread faster than BA.1, but it was unclear whether newcomers would also prove better at evading vaccines.
“BA.2 is probably worse than BA.1 — that’s the fear,” said Laith Abu-Raddad, an infectious disease epidemiologist at Weill Cornell Medical Center in Doha and co-author of the study.
Abu-Raddad and colleagues conducted a large-scale observational study using vaccination records and SARS-CoV-2 test results from the Qatari healthcare system. They found that Qatar residents who received two doses of the Pfizer-BioNTech or Moderna mRNA vaccine enjoyed months of substantial protection against symptomatic disease caused by BA.1 or BA.2.but weakened protection It only drops to around 10% after 4-6 months, which means that if all individuals are unvaccinated, the vaccine will only prevent 10% of cases.
Protection of BA.2 does not appear to diminish faster than protection of BA.1, and step up shooting Returns protection against symptomatic infection to 30-60% for either sub-variant. Monitoring data Data collected in the UK showed a similar trend: 25 weeks or more after the second dose of the vaccine, both sub-variants were less than 20% vaccine effective against symptomatic COVID-19, but in the third It rises to about 70% 2-4 weeks after a dose of vaccine.
The researchers also analyzed the degree of protection provided by the mRNA vaccine severe, but to do so they had to aggregate data on BA.1 and BA.2 cases – a necessary measure because Qatar’s population is heavily skewed towards young people, so severe COVID-19 cases are rare. It is only after pooling that researchers have enough cases to achieve meaningful results.
The analysis showed that protection against severe disease remained at 68% or higher for at least seven months, even in people who received only two doses of the vaccine, and spiked to more than 80% after a booster dose. Abu-Raddad said that since 70-80% of pooled cases are BA.2, he suspects that the vaccine could still provide high levels of protection against severe disease in the event of a spike in BA.2 levels.
in an email nature, Overall, the work is “a very reasonable study,” writes virologist Andrew Pekosz of Johns Hopkins University in Baltimore, Maryland. Qatar has always been in the lead.”
Abu-Raddad said the results gave him hope because a vaccine could prevent many of the most severe cases of COVID-19, even a reaction to BA.2. “Given the evolutionary challenges, vaccines actually work pretty well,” he said.
Pekosz agreed, adding in his email that the results underscore the importance of booster doses. “It is no longer enough to focus on primary vaccination programs. There must be programs to effectively vaccinate people through boosters,” he wrote.
But looking ahead, Abu-Raddad thinks researchers should shift from designing vaccines against a single variant to focusing on pan-coronavirus vaccines. “This will be a more fundamental solution in the future,” he said.
This article is reproduced with permission, first published March 18, 2022.