Several clinical trials are underway in which participants receive a first dose of one COVID-19 vaccine and a second dose of a vaccine made by a different drugmaker. The approach is being tested because it could help alleviate COVID-19 vaccine supply chain challenges, and the method could lead to a stronger immune response.
Researchers hope the mixing-and-matching approach, known as a heterologous prime-boost, will incite a stronger immune response than receiving two doses of the same vaccine type.
Below are three examples of trials testing the approach:
- University of Oxford researchers are conducting a trial, partially funded by the U.K. government, in which 830 participants receive a dose of Pfizer's COVID-19 vaccine followed by a dose of AstraZeneca’s shot, or vice versa. Pfizer's vaccine uses an mRNA platform and AstraZeneca's vaccine is based on an adenovirus.
- China’s National Institutes for Food and Drug Control is conducting trials that mix COVID-19 vaccine doses that are based on proteins, adenoviruses, RNA and coronaviruses that have been chemically inactivated, according to The New York Times.
- Russia's Gamaleya Research Institute of Epidemiology and Microbiology is testing its vaccine, Sputnik V, along with AstraZeneca's vaccine, both of which are based on adenoviruses.
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