In a new study from the Francis Crick Institute, researchers found a third ‘booster’ dose of COVID-19 vaccine successfully raises antibody levels that neutralize the Omicron variant.
They found that antibodies generated in people who had received only two doses of either the Oxford/AstraZeneca vaccine or the Pfizer/BioNTech vaccine were less able to neutralize the Omicron variant as compared to the Alpha and Delta variants.
They also found that antibody levels dropped off in the first three months following the second dose but that a third ‘booster’ dose raised levels of antibodies that effectively neutralize the Omicron variant.
In people who had received the Pfizer/BioNTech vaccine for all three doses, antibody levels against Omicron after a third dose were similar to those previously reached against Delta after only two doses.
Overall, antibody levels were nearly 2.5x higher against Omicron after three doses compared to after two.
Higher levels of antibodies against the Omicron variant were also found in people who received two doses of either vaccine and also reported previously having COVID-19 symptoms, compared to those who had not previously had COVID-19 symptoms.
Whilst levels of antibodies alone do not predict vaccine effectiveness, they are a very good indicator of protection against severe COVID-19.
This study confirms that three doses of the COVID-19 vaccine are essential to boost antibodies to quantifiable levels and maximize the amount of protection against severe disease and hospitalization.
In the study, the team analyzed 620 blood samples from 364 people who enrolled in the study.
Higher antibody titres (the greatest dilution level that still blocks 50% of virus infection in the lab) are a good predictor of vaccine efficacy and greater protection against COVID-19.
The team says people who have queued outside vaccinations centers should be reassured that a vaccine booster is the best way of protecting them from Omicron.
And for people who haven’t yet had a booster or even a first dose, it’s not too late.
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The study is published in The Lancet. One author of the study is Dr. Emma Wall.
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