With the two-dose regimen for vaccination against COVID-19 deemed as no longer offering an adequate level of protection against the disease, Thai health authorities are ramping up the administering of the booster or third dose. Meanwhile, Thailand’s top virologist has indicated that cross-vaccination produces very high immunity in inoculated individuals.
Dr. Yong Poovorawan, a virology expert at Chulalongkorn University’s Faculty of Medicine, cited a study jointly conducted by Oxford University and agencies in Brazil, published in The Lancet medical journal. He said the study found that full inoculation of an individual with an inactivated vaccine followed by a booster dose of either a viral vector or mRNA vaccine greatly heightens the individual’s immunity against Covid. Dr. Yong added that similar results have been obtained in studies in Sweden and Indonesia.
The head of Chulalongkorn University’s Center of Excellence in Clinical Virology also cited a study in Chile that sought to determine the efficacy of boosters doses which are administered to people inoculated with 2 doses of the CoronaVac (Sinovac) inactivated vaccine. In the study, the third doses comprised the CoronaVac, the AstraZeneca virus vector vaccine, and the Pfizer mRNA vaccine. The boosters were 78.8%, 93.2%, and 96.5% effective in preventing symptoms, respectively. They were 86.7%, 98.1%, and 96.8% effective in preventing deaths, respectively. Dr. Yong said this study was presented as a ’pre-print’ article in The Lancet.
The virology expert said the studies support the findings by his clinical virology center, which yielded similar results and are published on the MDPI platform. He added that the center will be submitting another study, this time relating to immunity against the Omicron coronavirus variant, this week. The study compares the efficacy of booster dose delivery at 3 months and 6 months after the date of administering the second shot. Dr. Yong said delivery 6 months after the second shot produced greater immunity, but comes with the downside of leaving a wider time window for the individuals to become infected.
Dr. Yong asserted that international-level studies have found that cross-vaccination produces very high immunity and is certainly be able to reduce the death rate from COVID-19. (NNT)
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