The UK’s decision to adopt a “mix and match” Covid vaccine booster strategy has been supported by a study showing that the mRNA shots from Pfizer and Moderna were by far the most effective at increasing antibody levels.
The Cov-Boost study, led by scientists at Southampton university, found that all the vaccines tested were safe and effective boosters. The Moderna vaccine increased the levels of antibodies the most, followed by the BioNTech/Pfizer shot, and even a half-dose of the Pfizer shot performed well. But the Oxford/AstraZeneca and Valneva jabs lagged.
Professor Saul Faust, who ran the trial, said the study also suggested that another key part of the immune system, T-cells, could be better at recognising new variants than antibodies. The study did not look at the Omicron strain.
“[The T-Cell response] does seem to be broader against all the various strains, which gives us hope that a variant strain of the virus might be able to be handled, certainly for hospitalisation and death if not prevention of infection, by the current vaccines,” he said.
The UK government decided to fuel its booster campaign with the mRNA jabs in September and expanded this strategy this week, buying an additional 114m doses from Pfizer and Moderna for the next two years. The UK’s Joint Committee on Vaccination and Immunisation received early data from this study in late August, before it issued its guidance.
Despite the AstraZeneca jab performing less well, Faust said it was a “very effective booster” and would be useful in countries without access to large supplies of mRNA jabs.
AstraZeneca said it was hard to draw conclusions from the study for many reasons, including because it was not known what antibody levels translate into protection against Covid-19. The drugmaker noted that the study showed that boosting with AstraZeneca resulted in higher antibody levels than in the trials for a two-dose regime.
The study also provided more evidence for why the UK government abandoned its €1.4bn deal with French vaccine maker Valneva.
Valneva’s own phase 3 trials showed it performed better than AstraZeneca’s vaccine as an initial dose. But the Cov-Boost study showed it was one of the least effective boosters. Valneva said it believed that the short interval between the second shot and the booster could have “adversely impacted” the results.
Confirmation of the efficacy of the strategy came as NHS England continued to finalise details of the country’s accelerated booster rollout three days after the announcement it was to be extended to over-18s and the interval between second and third doses halved to three months.
People with knowledge of the negotiations with general practitioners suggested the sticking point was whether NHS England would agree to pay them for certain activities, such as annual checks for people with diabetes and asthma, without submitting the paperwork to prove they had taken place.
In recognition that this money bankrolls vital staff such as practice nurses who might otherwise have to be let go, this flexibility prevailed at the height of the pandemic.
GPs say that if they are to carry out 75 per cent of vaccinations, as they have been doing, it must continue — even at the risk that a small minority of practices may take the payments without performing the work.
“GPs are seeing more patients than ever before and what we’re saying is if you want us to keep giving access to patients and deliver an enormous percentage of the vaccination programme, something’s got to give”, said one GP.