Everything you need to know about Covid-19 booster vaccines

The government’s scientific advisers are being pushed to press ahead with booster vaccinations for adults after they yesterday gave the green light for third jabs for patients with weakened immune systems.

Half a million people aged 12 and above who have not “generated a full response to their initial course of Covid vaccine” due to a severely weakened immune system will definitely be offered the third jab following the announcement, The Guardian said. Health officials have said that these “shots are not boosters… but instead form part of the primary vaccination schedule” for immunocompromised patients.

Professor Anthony Harnden, deputy chairman of the Joint Committee on Vaccination and Immunisation (JCVI), has said it is “highly likely” the UK will roll out a wider vaccine booster programme, adding that the plan will “be decided over the next few weeks”.

Appearing on BBC Radio 4’s Today programme, he continued “we are talking about boosting many, many millions of people and therefore we want to get the strategy right on this”, adding: “It’s just a question of how we frame it.”

Why are boosters needed?

The need for booster vaccines is largely down to waning effectiveness as no vaccine is 100% protective and almost all decline in effectiveness over time. Immunity among fully vaccinated people appears to ebb over time, with data from Israel, where 78% of people aged 12 and over are fully vaccinated, suggesting that there has been a large increase in infection rates in recent months.

The Middle Eastern nation is now “logging one of the world’s highest infection rates”, with nearly 650 new cases daily per million people, more than half of whom are fully vaccinated, according to Science.

Data from the Zoe Covid Study app has also suggested that vaccine protection against infection falls over time.

The study found that protection from two shots of the Pfizer-BioNTech jab “decreased from 88% at one month to 74% at five to six months”, while protection against infection after two Oxford-AstraZeneca jabs “fell from 77% to 67% at four to five months”, The Guardian said.

Professor Tim Spector, the lead scientist on the study, told Sky News: “In my opinion, a reasonable worst-case scenario could see protection below 50% for the elderly and healthcare workers by winter.”

Which vaccines will be used?

Harnden has said the JCVI is awaiting the results of the COV-Boost study, which is exploring the use of seven different types of Covid jab, and aims to discover which vaccines against Covid-19 are most effective as booster vaccinations. This may vary depending on which jab people had first.

The study could “shed light on whether a booster jab will have more effect if it involves mix-and-matching vaccines”, said the London Evening Standard, with patients possibly receiving a different vaccine than their initial jab. 

The vaccines currently being trialled are the Oxford-AstraZeneca, Pfizer-BioNTech, Moderna, Novavax, and Johnson & Johnson jabs, as well as French vaccine candidate Valneva and the first-generation vaccine candidate from Curevac.

The COV-Boost study also said it will be trialling the Novavax, Valneva and Pfizer-BioNTech vaccines as a half dose, as if it is found to be effective, “it could allow for double the number of vaccinations to be given using the same vaccine supply”. 

How effective are Covid-19 boosters?

The World Health Organization (WHO) has argued that a rush to roll out boosters is unnecessary until we have further data on their effectiveness and the best timings to administer them.

“We don’t understand who is going to need a booster, how long after their last dose, or which vaccine combination works best,” Bruce Aylward, a senior adviser at WHO, told Science, adding: “You need to understand all that before you decide how boosters should be used.”

But there have been some promising results from Israel, who rolled out booster shots for fully-vaccinated over-60s on 30 July “in a bid to curb an outbreak of the Delta variant”, reported Reuters.

According to a study released by Israel’s health ministry, a third dose of the Pfizer vaccine significantly improved protection from infection and serious illness compared to those who had only received two shots. 

Throughout August the booster program was gradually rolled out to more of the population, and third shots have been available to everyone over the age of 30 since 31 August.

Israelis are currently “required to wait five months after their second dose” before they can receive a booster, CNBC said. 

Who will be the first to get one?

The JCVI has previously said that the over-70s and extremely clinically vulnerable people should be included if a booster vaccination programme goes ahead, reported the BBC

And speaking to BBC Breakfast this week, Harnden said that as older people received vaccines a long time ago, their immunity is more likely to have “waned”. Ultimately, however, it is still uncertain who will be eligible to receive a booster shot and when the rollout might begin. 


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