Sinovac then AstraZeneca offers higher immunity than 2 doses of same brand
Cross-vaccination with Sinovac and then AstraZeneca can offer over three times more immunity than two AstraZeneca doses, according to results of a Thai study released on Thursday.
The results from a Department of Medical Sciences (DMS) study on vaccinated front-line medics deliver a big shot in the arm for Thailand’s cross-vaccination programme.
The study measured the immunity of 125 volunteers – front-line medics aged 18-60 (61 males and 64 females) – after receiving a dose of Sinovac then a dose of AstraZeneca, said DMS chief Dr Supakit Sirilak.
Their levels of immunity were then compared with immunity levels of people who received other combinations of the two vaccines, as measured by AU (Arbitrary Units).
Two Sinovac doses boosted immunity to around 117 AU while two AstraZeneca boosted it to 207. However, with the Sinovac-AstraZeneca cocktail, immunity soared to an average of 716.
Meanwhile, two shots of Sinovac followed by an AstraZeneca booster saw recipients’ immunity surge to 1700.
Data for the study came from the Bangkok metropolitan area, while the volunteers work at Siriraj Hospital. Data on immunity generated by Pfizer booster shots will be evaluated in one month, Supakit added.
The study also measured specific immunity against the Delta variant, which accounts for more than 90 per cent of new cases in Thailand. Using the Plaque Reduction Neutralisation Test , researchers found that two doses of Sinovac achieved a score of 24, which exceeds the standard (10) and is considered valid for eliminating the virus in vitro. Two injections of AstraZeneca were found to have an average of 76. This rose to 78 for cross-vaccination with Sinovac followed by AstraZeneca three weeks apart, which matched or exceeded the score for two doses of AstraZeneca. Medics double-jabbed with Sinovac followed by an AstraZeneca booster showed a score of 271, which is enough to combat Delta infection, said Dr Supakit.
He said side effects from the AstraZeneca booster matched those from two doses of AstraZeneca, with slight fever (66%), headache (33%) and fatigue (28%).
The study also included a small group of 14 people injected with two Sinovac doses followed by a Sinopharm booster. This cocktail generated only 2.5 times more immunity than two Sinovac doses.