The recommendation opposes India's decision to double the gap between two Covishield doses
The Pfizer Covid-19 vaccine is far less effective against the Indian (Delta) variant than against the original strain of the coronavirus, according to a recent study.
The antibody response to variants is much lower in people who have received their first jab and a longer gap between doses may lead to a significant shortage of antibodies against the deadly variant, according to the study published in The Lancet.
After a single dose of Pfizer-BioNtech vaccine, 79% people had quantifiable neutralising antibody response against the original strain. However, this declined to 50% for the B.1.1.7 or Alpha variant, 32% for Delta, and 25% for the B.1.351 or Beta variant first discovered in South Africa, reports NDTV.
The finding was revealed at a time when Bangladesh has taken stricter measures against the spread of the Indian variant, which is infecting a growing number of people in its border districts. The country received its first consignment of 100,620 doses of the Pfizer-BioNTech Covid-19 vaccine earlier this month.
The researchers note that it is most important to ensure that vaccine protection remains high enough to keep as many people out of the hospital as possible.
"Our results suggest that the best way to do this is to quickly deliver second doses and provide boosters to those who may not have high enough immunity against these new variants," said Emma Wall, UCLH Infectious Diseases consultant and Senior Clinical Research Fellow for the Legacy study.
The recommendation contradicts the Indian government's recent decision to increase the gap between two Covishield doses to 12 to 16 weeks from six-eight weeks; it cited studies that said the effectiveness of the vaccine increased with time.
However, critics accused the government of widening the gap to take the pressure off its vaccination drive, which has been stymied by a shortage of vaccine doses.
Sources in the government referenced "available real-life evidence particularly from the UK" that showed effectiveness was significantly higher at 81.3% (60.3-91.2) after two doses given at an interval of 12 weeks or longer, compared to 55.1 per cent (33-69.9) when given less than six weeks apart. That study, however, was not based on the Delta variant.
The latest Lancet study supports current plans in the UK to reduce the dose gap between vaccines, as it was found that people were less likely to develop antibody levels against the Delta variant compared to the previously dominant Alpha variant, first found in UK's Kent, after just one dose of the Pfizer-BioNTech vaccine.
Public Health England (PHE) said experts believe the Delta variant has overtaken the Alpha strain in the country and early evidence suggests there may be an "increased risk of hospitalisation" with the Delta strain compared to the Alpha.
Lancet says Pfizer-BioNTech's vaccine produces five times fewer antibodies against the Delta variant compared to those against the original Covid strain.
The vaccine produces fewer antibodies with increasing age and the levels decline over time, Lancet says.
The team, led by researchers from the Francis Crick Institute in the UK, analysed antibodies in the blood of 250 healthy people who received either one or two doses of the Pfizer vaccine up to three months after their first dose. The researchers tested the ability of antibodies to block entry of the virus into cells – "neutralising antibodies" -- against five different variants.