While the WHO still warns against the mix-and-match of COVID vaccines, many countries are already weighing, or have decided to adopt, such a solution. Domestic experts we interviewed say they believe mixing doses provides a more well-rounded protection and the trend is "inevitable" in the near future. The government needs to face this sooner rather than later.
As Taiwan's government won't allow mixed doses of COVID-19 vaccines, many seniors that got AZ for their first dose are taking matters into their own hands by going to mass vaccination stations to get Moderna for their second dose.
Doctors say COVID-19 will become seasonal shortly, which means mixed vaccine doses are inevitable and necessary. They say the Tsai administration needs to face facts sooner rather than later.
Wang Jen-hsien, Chair, Taiwan Counter Contagious Diseases Society:”AZ vaccines are recombinant adenovirus vector vaccines. Preexisting adenovirus antibodies in the body will go after the adenovirus from the second dose, so in theory, two doses of the AZ vaccine aren't as effective as a combination of AZ and BNT vaccines.”
Doctors say while AZ vaccines can produce both adenovirus and COVID-19 antibodies, Moderna and Pfizer only produce the latter. Therefore, many countries are experimenting with mixed doses of AZ with one of the other two.
Mixed doses are the trend in many countries. Doctors are therefore calling on the Central Epidemic Command Center to establish relevant guidelines, including the recommended amount of time between two differing vaccines.
Huang Li-min, Honorary Chair, Infectious Diseases Society of Taiwan:”The current belief is that the first dose of AZ followed by a second dose of an mRNA vaccine, especially BNT, provides the same level of protection as two doses of BNT. However, a mixed dose of AZ and BNT appears to offer a much higher level of protection than two doses of AZ.”
Research reports show that the first dose of AZ followed by a second dose of BNT or Moderna produces significantly more antibodies than two doses of AZ. Doctors say with so many people unwilling to get AZ vaccines in Taiwan, allowing mixed doses would greatly boost the willingness of people to get vaccinated and Taiwan's overall coverage rate.