Covid Letter: How's the world mixing its vaccines

India's drug regulator has approved a study to be conducted by the Christian Medical College (CMC), Vellore on the mixing of Covid-19 vaccines Covaxin and Covishield. The trial will involve 300 healthy volunteers. Separately, a recent study by the Indian Council of Medical Research (ICMR) involving 98 people, 18 of whom had inadvertently received Covaxin as the second dose after getting the first dose of Covishield in Uttar Pradesh, showed that combining these two Covid-19 vaccines elicited better immunogenicity than two doses of the same vaccine. The study also found that immunization with a combination of Covishield and Covaxin was safe and the adverse effects were also found to be similar when compared to the same dose regimen.

Covid Letter: How's the world mixing its vaccines

A trial

  • India's drug regulator has approved a study to be conducted by the Christian Medical College (CMC), Vellore on the mixing of Covid-19 vaccines Covaxin and Covishield. The trial will involve 300 healthy volunteers.


A study

  • Separately, a recent study by the Indian Council of Medical Research (ICMR) involving 98 people, 18 of whom had inadvertently received Covaxin as the second dose after getting the first dose of Covishield in Uttar Pradesh, showed that combining these two Covid-19 vaccines elicited better immunogenicity than two doses of the same vaccine.
  • The study also found that immunization with a combination of Covishield and Covaxin was safe and the adverse effects were also found to be similar when compared to the same dose regimen.


Around the world

A growing number of countries are considering switching to different Covid-19 vaccines for second doses or booster shots. Here are some:

  • Canada had been giving for some time a shot of Pfizer or Moderna mRNA vaccine to recipients of the first dose of AstraZeneca (same as Covishield). A few provinces went ahead first, amidst reports of rare blood clots in recipients of AstraZeneca shot, and later the national regulator cleared interchanging the dosing regimen.
  • Germany will in September begin offering a booster shot of mRNA vaccines to vulnerable individuals such as pensioners and people with weak immune systems, regardless of what their first dose was.
  • In Asia, Thailand, Cambodia, and Bahrain are giving vaccines approved in the West to recipients of Chinese vaccines of Sinopharm and Sinovac. While Bahrain is giving a second dose of Pfizer vaccine to those over 50 and vulnerable (obese or with weakened immune systems), Cambodia and Thailand are giving a second dose of AstraZeneca to anyone who had a first shot of the Chinese vaccine.
  • Others: Denmark, Russia, Indonesia, and South Korea have said interchanging vaccines was safe but are yet to approve it for the public.