Booster jab gives 90% Covid protection, study says

Booster doses of the Pfizer and Moderna vaccines offer improved protection against hospitalisations due to Covid-19 variants, new studies show.

Data released on Friday by the US Centres for Disease Control found that a third dose of either vaccine is more than 90% effective against both the Delta and Omicron variants.

The effectiveness of only two doses was found to wane to 57% after six months.

US officials have pleaded with the public to get boosted when eligible.

According to the CDC study, vaccine effectiveness against hospitalisation after two doses was 90% until six months after the second dose but fell to 81% afterwards.

Two weeks after the third dose, however, effectiveness against hospitalisation rose to 94%.

During the more recent surge in Omicron cases, the rate of effectiveness after two doses stood at 81% from the two weeks to six month-mark, before falling to 57%. Two weeks after the booster, effectiveness rose to 90%.

The CDC study was based on data from 88,000 hospitalisations in 10 US states.

A second CDC study, also released on Friday, examined data from 25 state and local health departments and found that people with booster shots are significantly less likely to get infected with Omicron.

The research found that among boosted patients, there were an average of 149 cases per 100,000 people, compared to 255 among those who had so far only had two doses.

A separate study, published in the Journal of the American Medical Association, determined that the chances of contracting Covid-19 and developing symptoms was 66% lower for those who have received a booster.

The spread of the Omicron variant of Covid-19 led to a record number of hospitalisations in the US. The number of hospitalised patients in the country currently stands at more than 150,000, surpassing a previous record set in January 2021.

In the Northeast of the country - including New York and Washington DC - the number of hospitalisations has since fallen, leading some experts to speculate that Omicron has begun to peak in some areas.

Officials warn, however, that other parts of the US may still be several weeks away from their peak.

Earlier this week, US President Joe Biden was asked why the definition of 'fully vaccinated' had yet to be changed to mean three shots, rather than two.

"You are better protected with the booster shot," he answered. "It's all part of the same thing."