Pfizer and Moderna jabs give best overall boost, UK trial finds

As reported by BBC News, the Pfizer and Moderna vaccines being used in the UK as boosters give the best overall boost response, according to a UK trial of seven different jabs

The trial is the first study of how well COVID booster jabs work and justifies the UK’s early decision to use these two vaccines for boosters. All the vaccines tested raised immunity against COVID to some degree. Researchers said there were promising signs the boosters would still protect against illness and death from Omicron.

To make vaccine supplies go further, even a half dose of Pfizer could be used to boost populations, they added. The trial results are thought to have prompted the UK to order an extra 114m doses of Pfizer and Moderna vaccines to be rolled out over the next two years. Boosters can cut the risk of infection by more than 93%. All adults aged over 18 in the UK are being offered a booster jab – usually either Pfizer or Moderna – while scientists find out more about the Omicron variant. Earlier this week, the head of Pfizer said boosters against COVID could become an annual event.

In the study of nearly 3,000 adults – led by the University of Southampton and published in the Lancet – boosters were given about three months after second doses of AstraZeneca or Pfizer, which is the gap now recommended in the UK. Out of seven different vaccines tested, all were found to be safe, and the side effects, including headache, fatigue.

All seven vaccines boosted immunity when given after two doses of Oxford-AstraZeneca, and six were effective following two doses of Pfizer – but some worked better than others. Overall, the mRNA vaccines – Moderna and Pfizer – gave the best boost to antibodies and T-cells, which are known to be important factors in how well vaccines work, particularly after two initial doses of AZ. The vaccines were equally effective in the over-70s and under-70s.

The researchers say they found a strong response to all variants of the virus, including Alpha, Delta and the original strain, and hope this will translate into protection against Omicron too. But they caution that further data will be necessary to work out what this means for long-term protection against serious disease.

In people who had received two doses of AZ, the study found a 30-fold rise in antibody levels after a Moderna booster, and a 25-fold rise after a Pfizer booster. After two doses of Pfizer, which offers higher baseline protection, the same vaccines raised antibody levels the most.

The researchers say they found a strong response to all variants of the virus, including Alpha, Delta and the original strain, and hope this will translate into protection against Omicron too. But they caution that further data will be necessary to work out what this means for long-term protection against serious disease.

In people who had received two doses of AZ, the study found a 30-fold rise in antibody levels after a Moderna booster, and a 25-fold rise after a Pfizer booster. After two doses of Pfizer, which offers higher baseline protection, the same vaccines raised antibody levels the most.