Paradoxically, this study showed that volunteers with lower doses on the first shot had better protection from COVID-19 than volunteers who received two full doses.
However, it was not clear whether the improvement in the low-dose vaccine was due to the dose itself, or to the fact that people who received the low-dose had a longer time between the first and second shots. .. -Boost interval.
Scientists at the Fineberg School of Medicine at the University of Northwestern have tested the efficacy of prime doses of the SARS-CoV-2 vaccine in mice, with a low-dose first shot followed by a full-dose booster shot that significantly improves SARS efficacy. Found to do-CoV-2 vaccine.
Studies have shown that booster shots have made it possible to generate more antibodies and T cells in mice and develop a much stronger immune response against SARS-CoV-2.
The findings were recently published in the journal Scientific immunochemistry.
Thoughts on “dose escalation” research questions in vaccine trials
Vaccine clinical trials use a method called dose escalation. In this method, one person is given a low dose and boosted with the same low dose. The second person receives a higher dose and is boosted with the same higher dose.
“Because of the idea of ensuring that the vaccine is safe, scientists use dose escalation to determine the’gold rock zone’. What is the minimum dose of vaccine that can be given to someone with a good immune response? The lead author, Pablo Penaloza-MacMaster, said Feinberg’s assistant professor of microbiology-immunology.
The northwestern study did not use the AstraZeneca-Oxford vaccine, but instead used a similar one. An adenovirus serotype 5 vaccine similar to the Can Sino developed in China and the Sputnik V vaccine developed in Russia. Penaloza-MacMaster said an ongoing study is considering this dosing regimen for the mRNA vaccine.
Why did the low / standard dose work so well?
In the AstraZeneca trial, participants who received the first full dose were boost-immunized approximately 3-4 weeks after the first injection, while participants who received the lower dose had a much longer prime boost interval. It was extended to.
A study from Northwestern University also reproduced this extended prime boost interval in mice and reported that increasing the prime boost interval improved the immune response.
“Extending the prime boost interval allows the immune system to rest and mature, allowing the immune response to expand more strongly during booster vaccination,” said Penaloza-MacMaster. “The longer you wait before boosting, the better your secondary immune response.”
However, this can be a tricky game. If you wait a long time to boost, you may become more susceptible to viruses.
“In the event of a pandemic, it is ethically difficult to extend the prime boost interval because it needs to be fully protected as soon as possible,” said Penaloza-MacMaster.
“But this approach may have the advantage of improving the endurance and size of the immune response in the long run, which is useful not only for SARS-CoV-2 vaccines, but also for other vaccines. maybe.”
The team also observed similar positive effects of reducing vaccine doses with experimental HIV vaccines based on adenovirus vectors, suggesting that these findings may be generalized to other vaccines.
Other authors of this study include Sarah Sanchez, Nicole Palacio, and Tanushree Dangi, members of the Penaloza-MacMaster Institute at Northwestern University.