Sunday Times (Sri Lanka)

‘Mixing and matching’ vaccines seem best strategy

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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

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