Vax Cocktail Endgame Against Covid-19

The world has been under the deadly spell of the coronavirus, with multiple waves of the pandemic decimating lives and economy in a fell swoop. In a record short span of time, numerous vaccines were developed to combat COVID-19. However, the ground reality seems, as per some experts, that administering a mix of vaccines presents better outcomes. Whether this approach holds good, needs a closer look.

- Ayesha Siddiqui

Vaccine mixing, which began unintentionally, is now gaining traction. There is a significant interest in mixing two different types of COVID-19 vaccines to mitigate against supply shocks or shortages that might otherwise reduce the speed of vaccine roll-out.

Canada which sort of started this trend unintentionally to manage its vaccine supply issues by allowing the mixing of vaccines. On June 1, 2021, the Canadian health agency, Health Canada asked those who had taken the Pfizer shot to take Moderna’s mRNA vaccine for their second dose. This has helped Canada overcome a supply bottleneck that delayed Pfizer doses in June.

Taking it even further, on June 17, 2021, the Canadian government recommended those who received the AstraZeneca (adenoviral vector-based vaccine) as the first dose should preferably take either the Pfizer or Moderna mRNA vaccine for their second dose. This decision was taken in light of the rare clotting events reported with the AstraZeneca vaccine.

Germany also followed suit by recommending the same AstraZeneca/Pfizer combo. The country reportedly allowed this heterologous approach on efficacy grounds.

In July 2021, Thailand became one of the first in Southeast Asia to officially start mixing vaccines. The country’s National Communicable Disease Committee issued a recommendation to give AstraZeneca jabs as the second dose to individuals who had initially received China’s Sinovac (based on inactivated virus technology), to build stronger immunity against the highly contagious delta variant which has created havoc in the country.

South Korea also introduced mix-and-match inoculations, using the AstraZeneca vaccine for the first dose and Pfizer for the second.