‘Mixing and matching’ vaccines seem best strategy
There is no question that Omicron is in
Sri Lanka and we have to watch out for its spread as it is more transmissible than Delta which wreaked havoc here, cautions Dr. Rajiva de Silva.
He says that ‘mixing and matching’ of vaccines seem to be the best strategy to beat this new variant and quotes a study of seven vaccines published in the scientific journal ‘Lancet’ in early December.
These vaccines can be categorized according to the levels of neutralizing antibodies and T-cell responses from the highest to the lowest:
The descending order for neutralizing antibodies –
Two doses of Pfizer topped with a booster of Moderna
Two doses of AstraZeneca topped with a booster of Moderna
Two doses of Pfizer topped with a booster of Pfizer
Two doses of Pfizer topped with a booster of Novavax
Two doses of AstraZeneca topped with a booster of Novavax
Two doses of AstraZeneca topped with a booster of AstraZeneca
For a T-cell response, the descending order was:
Two doses of AstraZeneca topped with Novavax
Two doses of AstraZeneca topped with Moderna
Two doses of Pfizer topped with Moderna Two doses of Pfizer topped with Pfizer Two doses of AstraZeneca topped with AstraZeneca
Two doses of Pfizer topped with Novavax “While mRNA vaccines (Pfizer and Moderna) produce neutralizing antibodies, the adenovirus-based vaccines (AstraZeneca) are useful in the T-cell response. So Sri Lankans have got a good deal,” says Dr. de Silva, adding that as there are no data worldwide on Sinopharm “we don’t know much” about mixing and matching with this vaccine. Meanwhile, Dr. de Silva adds that studies in Chile have shown that boosting with either a Pfizer or AstraZeneca had a better effec
tiveness than boosting with Sinovac (an inactivated vaccine similar to Sinopharm) in people given 2 primary doses of Sinovac. This was, however, before the advent of Omicron.
The WHO has recommended based on availability to administer:
An mRNA/vectored vaccine (Pfizer, Moderna/ AstraZeneca) booster to those given inactivated vaccines
An mRNA booster to those given vectored vaccines
Vectored vaccine booster for those given mRNA vaccines