The United Kingdom has expanded a controversial trial to mix-and-match first and second doses of different vaccines to the Moderna and the Novavax shots as it attempts to find out if such a strategy might offer better, longer-lasting immunity while allowing more flexibility in the rollout.
The Oxford Vaccine Group study will now allow adults over 50 who have received a first dose of the Pfizer or AstraZeneca vaccine to apply to take part in the study.
According to the BBC, the study plans to recruit around 1,050 volunteers who had already received a shot in the past eight to 12 weeks and participants may either receive the same shot as their first dose or a shot of the Moderna or Novavax vaccine.
After receiving the second dose, the participant’s blood will be examined to check the robustness of their immune response triggered by the vaccines.
The trial aims to examine if the mixed approach will generate an immune response that is as good or better than the standard two-dose approach.
A positive result from the study could help governments around the world juggle constrained supplies of vaccines, and blend the strengths of the AstraZeneca shot, which is based on traditional vaccine technology, and Moderna and Pfizer’s experimental mRNA vaccines.
The Moderna vaccine began rolling out in the U.K. this week and the Novavax shot—which will be manufactured in the U.K. by GlaxoSmithKline (GSK)—is currently being reviewed by the U.K.’s medicines regulator.
What To Watch For
The first leg of the study started earlier this year with more than 800 people taking part. The participants of that study have received two doses of either the Pfizer vaccine, the AstraZeneca vaccine or a mix. Results of this first trial are expected next month and the expanded trial will share its primary findings either June or July. The study is expected to run for a year.
Mix-and-match strategies have been used for decades for vaccines for other illnesses but this strategy remains unproven for Covid-19. The U.K’s initial study in January faced some backlash from the medical community while the CDC guidelines currently recommend against using a different vaccine for a first and second shot. The results of the study will be watched keenly in Europe where millions of people have received a first shot of the AstraZeneca vaccine but now France and Germany have recommended those aged under 50 should take a second shot of a different vaccine following rare incidents of blood clots linked with the British-Swedish drugmaker’s vaccine. Russia’s Sputnik V Vaccine is designed around using two slightly different doses and has proven to be 92% effective in preventing Covid-19 symptoms.
Scientists Test a New Covid-19 Vaccine Question: Mixing Different Doses (Wall Street Journal)