Britain opting for mixand-match vaccinations
Interchangeability of dose distribution is not data driven
Amid a sputtering vaccine rollout and fears of a new and potentially more transmissible variant of the coronavirus, Britain has quietly updated its vaccination playbook to allow for a mix-and-match vaccine regimen. If a second dose of the vaccine a patient originally received isn’t available, or if the manufacturer of the first shot isn’t known, another vaccine may be substituted, health officials said.
The new guidance contradicts guidelines in the United States, where the Centers for Disease Control and Prevention has noted that the authorized COVID -19 vaccines “are not interchangeable,” and that “the safety and efficacy of a mixed-product series have not been evaluated. Both doses of the series should be completed with the same product.”
Some scientists say Britain is gambling with its new guidance. “There are no data on this idea whatsoever,” said John Moore, a vaccine expert at Cornell University. Officials in Britain “seem to have abandoned science completely now and are just trying to guess their way out of a mess.”
Health officials in Britain are caught in a deadly race with the virus, which is surging again, and are struggling to get as many people vaccinated as possible. Hospitals continue to strain under a crush of coronavirus patients, and tens of thousands of new infections are reported each day. Schools in London and other regions hit hard by the virus will remain closed for at least the next two weeks, government officials said Friday.
The country has issued an emergency green light to two vaccines, developed by Pfizer and Astrazeneca. According to Britain’s new guidance, “every effort should be made” to complete a dosing regimen with the same shot first used. But when “the same vaccine is not available, or if the first product received is unknown, it is reasonable to offer one dose of the locally available product” the second time around.
“This option is preferred if the individual is likely to be at immediate high risk or is considered unlikely to attend again,” the recommendation said. Because both vaccines target the spike protein of the coronavirus, “it is likely the second dose will help to boost the response to the first dose.”
But it is far from certain that the vaccines are so interchangeable, several researchers said.
“None of this is being data driven right now,” said Dr. Phyllis Tien, an infectious disease physician at the University of California, San Francisco. “We’re kind of in this Wild West.”
Steven Danehy, a spokesman for Pfizer, pointed to the company’s late-stage clinical trial findings, which relied on a two-dose schedule of its vaccine that was 95 percent effective at preventing COVID -19.
“While decisions on alternative dosing regimens reside with health authorities, Pfizer believes it is critical health authorities conduct surveillance efforts on any alternative schedules implemented and to ensure each recipient is afforded the maximum possible protection, which means immunization with two doses of the vaccine,” Danehy said.
Representatives of Public Health England and Astrazeneca did not respond to requests for comment.