Preliminary results indicate that mixing COVID-19 vaccines can boost immune response.
A study in Spain, led by the Carlos III Health Institute in Madrid, found that over 600 people vaccinated with the Oxford/AstraZeneca vaccine followed by the Pfizer/BioNTech vaccine produced a good immune response. The data suggested that mix and match vaccines may give higher antibody levels than two doses of a single vaccine.
A U.K. study called for a similar strategy, saying that people vaccinated with mix-and-match products had mild to moderate common vaccine-related side effects comarted to those who received two doses of the same vaccine. These side effects were short-lived, and there were no other safety concerns.
The Canadian government is now advising that younger people who got their first dose should receive an alternative vaccine as their second dose, most commonly mRNA vaccines such as Pfizer's.
Other countries such as Germany, France, Sweden, Norway, and Denmark have also recommended mixing vaccines, though the Centers for Disease Control and Prevention (CDC) only suggests alternating vaccines only under exceptional situations.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19, including symptoms, prevention, and available treatment, please refer to the World Health Organization or your national healthcare authority.