Study shows impact of boosters on protection against Omicron

Tamaki Makaurau - Traditional regimens of covid vaccines do not neutralise the fast-spreading Omicron variant according to a new combined MGH Institute of Health Professions, Massachusetts Institute of Technology and Harvard study.

Individuals who received three doses of the mRNA vaccine had very significant neutralisation against the Omicron variant, as opposed to those with two doses.

An additional booster dose vaccine is needed to provide immunity against the Omicron variant, according to a study by researchers at the Ragon Institute of MGH, MIT and Harvard.

The results of the study, reported in the journal Cell, indicate that traditional dosing regimens of covid vaccines do not produce antibodies capable of recognising and neutralising the Omicron variant.

The variant, given the name Omicron by the World Health Organization, would soon prove to be far more transmissible than Delta, the variant that previously had caused the majority infections.

People wanted to know whether current vaccines protect against Omicron so researchers collaborated .

The first step was to construct a harmless version of Omicron known as a pseudovirus that could be used in the laboratory to evaluate the effectiveness of the Pfizer and Moderna injections and the one-dose Johnson & Johnson vaccine.

The pseudovirus mimicked the behaviour of Omicron, which has 34 mutations on its spike protein that are not found on the original strain first detected in Wuhan, China, in December 2019.

Scientists believe that these mutations may be partially responsible for Omicron’s rapid spread throughout the world.

They then acquire blood samples from 239 individuals who had been fully vaccinated with one of the three vaccines.

Included in the group were 70 men and women who had received a third booster dose of either the Pfizer or Moderna vaccine.

The blood samples were used to measure how effectively each vaccine induces production of protective immunity in the form of antibodies against the Omicron pseudovirus, as well as the Delta and wild type viruses.

The results were striking. The researchers detected very little neutralisation of the Omicron variant pseudovirus when they used samples taken from people who were recently been double vaccinated. But people who received three doses including the booster had very significant neutralisation against the Omicron variant.

It’s not yet clear why a booster dramatically improves immune protection against Omicron, but researchers say one possibility is that an additional dose creates antibodies that bind more tightly to the spike protein, increasing their effectiveness.

Also, a booster dose may generate antibodies that target regions of the spike protein that are common to all forms of covid.