Dr Yong Poovorawan, chief of the Center of Excellence in Clinical Virology at Chulalongkorn University, said vaccines for many diseases had low disease prevention efficacy rates, but could prevent illness and death.
He was speaking during an interview broadcast on the National Broadcasting Services of Thailand (NBT) TV channel yesterday afternoon.
The interview followed reports that Brazil found the COVID-19 prevention efficacy rate of the Sinovac Biotech of China vaccine to be just 50.4%. The Thai government has ordered 2 million doses of Sinovac’s COVID-19 vaccine.
Dr Yong said Brazil trialled the vaccine on 10,000 medical workers who were always at high risk of infection. Naturally, efficacy rates were lower among at-risk people and higher among the general population, he said.
Sinovac’s vaccine showed disease prevention efficacy rates of 65% during its trial in Indonesia, 90% in Turkey, 86% in the United Arab Emirates and over 70% earlier in Brazil, when it was trialled in the general populace, not medical workers only, he said.
He insisted that he had no conflict of interest with any COVID-19 vaccine producer, and was not speaking in favour of the government.
The World Health Organization accepted any COVID-19 vaccine with an efficacy rate of over 50%.
Despite lower efficacy in disease prevention, medical authorities gave vaccines because they could prevent infected people falling ill and dying. About 30 million doses of COVID-19 vaccines were used worldwide, Dr Yong said.
He also said it took at least five years to determine whether a new vaccine would be safe for general vaccination.
There were 10 COVID-19 vaccines that had been trialled for a few months and given to people for 3-4 months, and all manufacturers would have to continue studying the effects, Dr Yong said.
No one could now tell how long the effect of a COVID-19 vaccine would last, he said.
Vaccination for the time being was aimed at containing the pandemic crisis, he said.
He suggested the government acquire samples of COVID-19 vaccines it had already ordered for early trials with local people, to study their effects before accepting the ordered vaccines.
Dr Yong said he put out questionnaires through his social media account, and most of the 30,000 respondents said they were ready for COVID-19 vaccination.