The efficacy of any vaccine, including COVID-19 vaccines, tends to be lower when used in the field to inoculate millions of people, when compared to the results produced during clinical trials, said Thai virologist Dr. Yong Poovorawan in his Facebook post on Friday.
He cited the case of a Hepatitis B vaccine, which its manufacturer claimed had efficacy of between 94-95%. When the vaccine was used in mass inoculations, however, its efficacy dropped to about 80%.
Likewise, he said, the 95% efficacy of a COVID-19 vaccine, asclaimed by Pfizer during the trial period, is likely to drop due to several variables.
About 30% of the population of Israel have already been inoculated using the Pfizer vaccine, said Dr. Yong, adding that the actual mass efficacy of this vaccine will be known soon.
Likewise, he said that the real efficacy of the Chinese vaccine, Sinopharm, which has been injected to about 20% of the population of the United Arab Emirates, will also be known shortly.
He recommended that Thai people do not rely on vaccines alone, even when the vaccines are available, but to protect themselves by strictly observing basic safety standards, namelywearing face masks all the time while outdoors and in crowded places, regularly washing their hands with sanitizer and maintaining social distancing.
Thailand has placed orders for 26 million doses of vaccine from AstraZeneca and for the Sinovac vaccine from China.