People who have received the Pfizer vaccine have been issued a crucial update concerning the Indian variant of Covid-19.

New research suggests those who have received the jab have lower antibodies targeting the strain of coronavirus.

The Pfizer/BioNTech vaccine is primarily being given to under-30s in the UK due to the link between the AstraZeneca jab and blood clotting.

The Indian variant is now believed to be dominant in the UK, with early evidence suggesting it may lead to an increased risk of being admitted to hospital compared with the Kent variant.

A total of 12,431 cases of the mutation have been confirmed in the UK up to June 2, according to Public Health England.

This up 79% from the previous week’s total of 6,959.

The research also suggests the levels of these antibodies are lower with increasing age and that levels decline over time.

Researchers say this provides additional evidence in support of plans to deliver a vaccination boost to vulnerable people in the autumn.

The new laboratory data from the Francis Crick Institute and the National Institute for Health Research (NIHR) UCLH Biomedical Research Centre also supports current plans to reduce the dose gap between vaccines.

The study found that after just one dose of the Pfizer jab, people are less likely to develop antibody levels against the Indian (B.1.617.2) variant, also known as Delta, as high as those seen against the previously dominant Kent variant (B.1.1.7) also known as Alpha.

However, levels of antibodies alone do not predict vaccine effectiveness and prospective population studies are also needed.

Lower neutralising antibody levels may still be associated with protection against Covid-19, the experts say.

Emma Wall, UCLH Infectious Diseases consultant and senior clinical research fellow for the Legacy study, said: “This virus will likely be around for some time to come, so we need to remain agile and vigilant.

“Our study is designed to be responsive to shifts in the pandemic so that we can quickly provide evidence on changing risk and protection.

“The most important thing is to ensure that vaccine protection remains high enough to keep as many people out of hospital as possible.

“And our results suggest that the best way to do this is to quickly deliver second doses and provide boosters to those whose immunity may not be high enough against these new variants.”

The Research Letter published in The Lancet states: “These data, together with epidemiological data of B.1.617.2 growth, raise the possibility that this VOC (variant of concern) presents a dual challenge of reduced vaccine efficacy akin to the B.1.351 VOC, and increased transmissibility beyond the B.1.1.7 VOC.”

Eleanor Riley, professor of immunology and infectious disease, University of Edinburgh, said: “These data cannot tell us whether the vaccine will be any less effective at preventing severe disease, hospitalisation and death; we need to wait for the actual data on these outcomes.”