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Covid-19: Medical community split over vaccine interval policy as WHO recommends six weeks

BMJ 2021; 372 doi: (Published 25 January 2021) Cite this as: BMJ 2021;372:n226

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  1. Elisabeth Mahase
  1. The BMJ

The medical community appears to be split over whether the UK has made the right decision in delaying the second Pfizer BioNTech vaccine dose from three weeks to 12, in order to administer more first doses of the vaccine to people who are at risk.

The UK has become isolated from other countries in terms of vaccine policy, with most others vaccinating at either the intended three week interval or extending the interval to the World Health Organization recommended six weeks.

The UK government announced at the end of December that the interval between vaccine doses would be extended to 12 weeks, despite clinical trials of the Pfizer BioNTech vaccine using a 21 day gap.1 At the time, concerns were raised over the lack of evidence for the interval and the potential for vaccine resistant variants to develop. The four UK chief medical officers said, however, that the move would “protect the greatest number of at risk people in the shortest possible time,” while reducing the strain on the health service.

The British Society for Immunology also appeared to support the move, saying that most immunologists would agree that the delay would be unlikely to have a negative effect on the overall immune response post-boost.

However, the BMA has since written to chief medical officer for England Chris Whitty asking him to bring the interval down to the six week (42 day) maximum suggested by WHO. A BMA spokesperson told The BMJ that the letter raised growing concerns from the medical profession regarding the delay of the second dose as well as worries that “given the unpredictability of supplies, there may not be any guarantees that second doses of the Pfizer vaccine will be available in 12 weeks’ time.” They said, “The BMA supports giving a second dose up to 42 days after the first dose, in line with international best practice as this would still allow for a doubling of the numbers of people protected by vaccination within a given time period compared with the original three week dose interval. The association is urging the chief medical officer to review the UK’s current position of second doses after 12 weeks.”

In an opinion piece2 in the Telegraph, however, deputy chief medical officer Jonathan Van-Tam said, “Some people are questioning the UK policy of trying to give as many at risk people as possible the first dose of vaccine in the shortest possible time, inevitably extending the interval before the second dose is given.

“But what none of these—who ask reasonable questions—will tell me is: who on the at risk list should suffer slower access to their first dose so that someone who’s already had one dose, and therefore most of the protection, can get a second? Everyone on the priority list is at risk from this virus, and vaccines just can’t be produced at an unlimited rate.”

WHO recommendation

WHO has acknowledged that some countries are facing “exceptional circumstances” and may want to delay second doses to “allow for a higher initial coverage.” But it said that there is no data on efficacy beyond 42 days, as trial participants received two doses with an interval between doses in the trial ranging from 19 to 42 days.3

“Countries experiencing exceptional epidemiological circumstances may consider delaying for a short period the administration of the second dose as a pragmatic approach to maximising the number of people benefiting from a first dose while vaccine supply continues to increase. WHO’s recommendation at present is that the interval between doses may be extended up to 42 days, on the basis of currently available clinical trial data,” WHO said.

Following the recommendation, some EU countries including Denmark, France, and Germany have decided to administer the second Pfizer dose three to six weeks after the first.

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