london a third dose of covid19 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 omicron after a third dose were similar to those previously reached against delta after only two shots overall antibody levels were nearly 25 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 covid19 symptoms compared to those who didnt 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 covid19 the researchers noted the study confirms that three doses of covid19 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 and for people who havent yet had a booster or even a first dose its not too late emma said in a statement the researchers analysed 620 blood samples from 364 people who enrolled in the study they tested the ability of antibodies to block entry of the virus into cells so called neutralising antibodies against different variants of sarscov2 including omicron the researchers also included synthetic neutralising antibodies that are currently in use for covid19 treatment to test if they have neutralising activity against variants of sarscov2 the team found that xevudy sotrovimab a recentlyapproved synthetic monoclonal antibody used to prevent and treat patients at risk of developing severe covid19 was able to neutralise the omicron variant we have really important early data to suggest that at least some versions of synthetic antibodies that we currently use to treat certain patients are likely to be effective against this new variant bryan williams uclh director of research added david lv bauer from francis crick institute said while omicron has considerably more mutations than other recent variants such as alpha and delta the study shows that the boosters push the immune system to make a broad response capable of tackling it this new variant can overcome the immune blockade put