U.K. Defends Vaccine-Dose Delays as Approach Gains Traction

The U.K. defended its decision to delay second doses of vaccines as the best way to combat the coronavirus, while more countries adopt a similar strategy in a race against rising cases and new strains.

U.K. Health Secretary Matt Hancock said Sunday there is high confidence the first dose provides “decent efficacy” against the virus and that the country’s plan will speed vaccinations across the country.

“You want to get as many people to have as much protection as possible, as quickly as possible,” Hancock said in an interview on Sky News. “This is the way to save most lives fastest.”

Governments around the world are scrambling to revise vaccination programs as research shows strains from the U.K., South Africa and Brazil to be more contagious or possibly even more lethal than the original virus. And countries are tightening restrictions on international travel as scientists assess whether the existing vaccines are as effective against the variants.

Supply issues are also hampering vaccine rollouts, adding to pressure to give first shots to as many people as possible rather than holding doses back to complete the two-course regimen sooner. Both AstraZeneca Plc. and Pfizer Inc. have said they won’t be able to meet delivery targets to Europe in the coming weeks, adding to the pressure to stretch existing supplies. States across the U.S. have also had to slow their vaccine drives because of difficulties in obtaining doses.

France on Saturday recommended doubling the amount of time to six weeks between the first and second shots, concluding that would lead to at least 700,000 more people being inoculated in the first month.

The move toward longer dosing intervals could double the number of people who gain some protection against the virus in the near term but carries risks. It’s unclear how much benefit a single shot of the vaccines currently available will offer, and there’s a danger that mutations could flourish if immunity wanes after a first dose.

The new French advice is for the vaccine made by Pfizer and BioNTech SE as well as another supplied by Moderna Inc.. Pfizer recommends that people should receive their second dose within a three-week period, while Moderna advises a second shot within four weeks.

France’s move came after a Jan. 21 statement from the U.S. Centers for Disease Control and Prevention that follow-up doses of Covid-19 vaccines could be given up to six weeks later if it’s not feasible to get them in the recommended interval. The U.S. Food and Drug Administration also offered some flexibility for “modest delays.”

Research from Israel, which leads the world in vaccinations, shows that two days after a second shot, new infections and hospitalizations were both down about 60% from their peak. In an encouraging sign for the move to delay second doses, however, trends began to shift around two weeks from the first shot.

The U.K. has already extended the maximum wait time from three weeks to 12 weeks as Boris Johnson’s government seeks to vaccinate 15 million people by the middle of February. The U.K. is also vaccinating with the shot developed by AstraZeneca, which was most effective when administered with a gap of up to 12 weeks.

The U.K. has already administered more than 6 million doses, the most in Europe and Johnson tweeted Saturday that every shot brings the U.K. closer to beating the virus. In France, just over 1 million people have been vaccinated.

Delays to dosing regimens are facing new questions from doctors, with the British Medical Association calling for the U.K. to “urgently review” its decision allowing the delay to the second dose of the Pfizer-BioNTech vaccine.

The BMA said in a statement that it supported delays of up to 42 days, or six weeks, citing international guidance from the World Health Organization that this could work, but warned that Britain’s plan goes “well beyond” that.

“BMA members are also concerned 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,” the group said in a statement.

The WHO has said there’s no data to support the U.K.’s move but has said changes in dosing regimes could be justifiable in emergency situations.

In its recommendation, the U.S. CDC said, there is “limited data on efficacy” of the Pfizer and Moderna vaccines beyond the six-week interval, according to the guidance, but if the second dose is administered later, “there is no need to restart the series.”