Everything you need to know about Covid booster vaccines

Boris Johnson has urged all those eligible to book their Covid-19 booster jabs, describing vaccines as “our way through this winter”.

Stressing the importance of a third dose, the prime minister said that “to keep yourself, your loved ones, and everyone around you safe, please get your booster when you get the call”.

“This is a call to everyone, whether you're eligible for a booster, haven’t got round to your second dose yet, or your child is eligible for a dose - vaccines are safe, they save lives, and they are our way out of this pandemic,” he added.

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The intervention came after the prime minister “piled pressure on vaccine chiefs” to shift the date for boosters forward, The Times said. Bringing forward the date would mean an additional nine million people would become eligible for a third jab, the Daily Mail added.

Why are boosters needed?

Scientists say booster vaccines are necessary because of the waning effectiveness of previous jabs. No vaccine is 100% protective and almost all decline in effectiveness.

Immunity among fully vaccinated people appears to ebb over time. Data from Israel — where 87.2% of people aged 12 and over are fully vaccinated — suggests that there has been an increase in infection rates in recent months.

With more infectious variants also cropping up since the outbreak of the pandemic, experts also believe that existing vaccines may not be sufficient in the long run.

How effective are they?

The first full trial of the Pfizer jab’s booster efficacy found that a third shot is 95.6% more effective than two shots and a placebo at preventing infection. A researcher involved told the Financial Times that the data represents a “big step forwards”.

Other vaccines are also effective when deployed as a booster. Moderna was found to provide “higher neutralizing antibody titers” against the Delta variant when administered as a third jab, according to phase two trial results.

And preliminary results suggest a Johnson & Johnson “booster shot elicited a rapid and robust increase in spike-binding antibodies”, according to News Medical.

The Oxford-AstraZeneca vaccine will not be used in the UK’s booster rollout. However, “the few trials to have tested extra doses” suggest the jab “prompted a spike in levels of infection-blocking ‘neutralizing’ antibodies”, according to Nature.

Margaret Harris, a spokesperson for the World Health Organization, has warned that vaccines alone are not enough to stop the spread of Covid-19.

“The problem is focusing on one thing, the vaccine isn’t going to get us out of this,” she said during an interview on Times Radio. Instead, “other measures” are needed in conjunction with vaccines, including “wearing masks when you’re indoors”.

Who can have one?

A booster jab will be offered to everyone over 50, as well as younger people with health conditions that mean they are more at risk from infection.

Frontline medical staff will also be offered a third shot. A full list of who is eligible for a booster can be found here.

Is the rollout going too slowly?

There are currently approximately 8.5m people in the UK who are eligible for a booster.

But the latest NHS data shows only 3.7m have so far taken up the offer of a third dose, leaving 4.8m who qualify but have not yet received a top-up.

Amanda Pritchard, chief executive of the NHS, has welcomed a string of record setting days for booster vaccinations. Saturday “was the biggest day yet for Covid booster jabs”, she tweeted, adding: “More than 325,000 people getting vital protection.”

Saturday’s figures, when combined with the number of jabs delivered on Thursday and Friday, meant more than 800,000 people received a booster over three days.