Government urged to ramp up jabs within three months Government urged to ramp up jabs within three months THAILAND: The government has been urged to carry out its mass vaccination drive against COVID-19 within three months, after a recent study found a single dose of the vaccine can increase immunity against the virus by 96.7%. Photo: Bangkok Post. Renowned virologist Yong Poovorawan wrote on his Facebook page yesterday (May 3) that a study conducted on Thais who had received one shot of the AstraZeneca vaccine showed a 96.7% improvement in immunity against the virus when compared to unvaccinated individuals, while those who have recovered from COVID-19 between 4-8 weeks prior to testing showed a 92.4% improvement in immunity. The study was carried out on 61 individuals for one month after they received their first shot.