Study says booster gives effective antibody shield

London, Jan. 20: A third dose of Covid-19 vaccine increases the level of antibodies that can effectively neutralise the Omicron variant of Coronavirus, according to a study published in The Lancet journal.

Researchers from Francis Crick Institute and the National Institute for Health Research (NIHR), UK, found that antibodies generated in people who had received only two doses of either the AstraZeneca or the Pfizer vaccine were less able to neutralise Omicron as compared to Alpha and Delta variants.

They also found that antibody levels dropped off in the first three months following the second dose but a third booster dose raised levels of antibodies that effectively neutralise the Omicron variant.

The study found that in people who had received the Pfizer vaccine for all three doses, antibody levels against the Omicron variant of Covid-19 after a third dose were similar to those previously reached against Delta after only two shots.

Overall, antibody levels were nearly 2.5 times higher against Omicron after three doses compared to after two jabs, according to the researchers.

Higher levels of antibodies against Omicron were also found in people who received two doses of either vaccine and also reported previously having Covid-19 symptoms, compared to those who didn’t have disease symptoms in past.

While levels of antibodies alone do not predict vaccine effectiveness, they are a very good indicator of protection against severe Covid-19, the researchers noted.

The study confirms that three doses of Covid-19 vaccine are essential to boost antibodies to quantifiable levels and maximise the amount of protection against severe disease and hospitalisation.

“People who have queued outside vaccinations centres should be reassured that a vaccine booster is the best way of protecting them from Omicron,” said Emma Wall, an infectious diseases consultant at UCLH Biomedical Research Centre of NIHR.