Do You Know What The 65.3 Percent Efficacy Of The Sinovac Vaccine Means? Why 'Lost' To Pfizer And Moderna?

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JAKARTA - The Food and Drug Supervisory Agency (BPOM) said the results of phase III clinical trials, the COVID-19 vaccine made by a Chinese pharmaceutical company, Sinovac, had an efficacy or efficacy level of the Sinovac corona vaccine of 65.3 percent. On this basis, BPOM has officially issued a permit for the emergency use of the COVID-19 vaccine or emergency use authorization (EUA).

But do you know what the 65.3 percent efficacy means, how to calculate it, and why is Sinovac's efficacy lower than its competitors Pfizer and Moderna, which touched 90 percent?

Here is the explanation of Prof. DR Zullies Ikawati, Apt, Professor of the Faculty of Pharmacy, Gadjah Mada University (UGM).

According to him, a vaccine with 65.3 percent efficacy or efficacy in clinical trials means a 65.3 percent reduction in disease cases in the vaccinated group compared to the unvaccinated (or placebo) group.

"And it was found in a controlled clinical trial," said Zullies Ikawati in an electronic message received by VOI editorial, Tuesday, January 12.

For example in the Sinovac clinical trial in Bandung which involved 1600 people. There were 800 subjects who received the vaccine and 800 subjects who received a placebo (blank vaccine). If from the vaccinated group, 26 were infected (3.25%), while in the placebo group there were 75 people who contracted Covid (9.4%).

"So the efficacy of the vaccine is 0.094 - 0.0325 / 0.094 x 100% = 65.3%. So what determines is the ratio between the vaccinated group and the group that is not," he explained.

Efficacy will be influenced by the characteristics of the test subjects. If the test subjects are the high-risk group, it is likely that the placebo group will be more exposed, so that the calculation of the efficacy is increased.

Well, clinical trials in Brazil use a high-risk group, namely health workers, so that the efficacy is higher. Meanwhile, in Indonesia it uses the general population with a smaller risk.

"If the test subjects are at low risk, let alone adhere to the health program, never leave the house so that not many are infected, then the comparison of the incidence of infection between the placebo group and the vaccine group will be lower, resulting in a lower number," he explained.

According to Zullies Ikawati, when the BPOM announced the efficacy result of Sinovac of 65.3 percent was a good start even though there were voices asking why only 65.3 percent.

But health organizations, the World Health Organization (WHO), the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have put vaccine approvals at 50 percent. This means that, epidemiologically, reducing the incidence of infection by 50% is meaningful and saves the lives of many people.

"Moreover, we also mentioned earlier that the vaccine has high immunogenicity with a seropositive rate of 99.23% in the first 3 months, which means it can trigger antibodies in the subjects who received the vaccine," he explained.

"Of course we still have to wait for the effectiveness of the vaccine after it is used in the community. And keep in mind that because this is only EUA from the interim report, observations on the efficacy and safety will still be carried out for the next 6 months to get full approval," he said.