How much will the Chinese CoronaVac vaccine really count in fighting the pandemic?

Although the results on its effectiveness are mixed, the Chinese CoronaVac vaccine could still reduce severe cases and deaths from Covid-19, particularly in countries with the largest outbreaks

(photo: Getty Images) effectiveness of the CoronaVac coronavirus vaccine, developed by the Beijing company Sinovac Biotech and studied in China, Brazil, Indonesia and Turkey, there are still many doubts. Initially, in fact, its effectiveness in preventing Covid-19 was estimated by researchers from the Butantan Institute at approximately 78%. A significantly lower percentage than that of other vaccines, such as that of Pfizer and Moderna, equal to about 90%. And that only recently, as we told you a few days ago, it would be further reduced to 50.4%, therefore close to the minimum threshold (equal to 50%) recommended by the World Health Organization (WHO) and necessary to receive the 'approval. Nature also talks about it, according to which the data on CoronaVac would be rather conflicting in the different countries where it is being tested, even if this vaccine, which is based on the inactivated virus, could still help reduce cases of severe forms of Covid-19 and deaths, especially in those areas where the greatest outbreaks occur.

The researchers of the Butantan Institute, as the magazine tells us, have specified that their initial estimate was based on partial data and restricted criteria, i.e. it did not concern patients with mild forms (and who therefore have now reduced the percentage to 50.4%). From their study, which has not yet been reviewed, it emerged that out of about 250 cases of Covid-19, 167 had received a placebo and 85 had been vaccinated. And that none of the latter had developed a severe form of the disease and needed hospitalization. "The data from Brazil is important for Turkey, which yesterday launched the plan to distribute millions of doses of CoronaVac under an emergency use authorization announced on January 13," comments Murat Akova, a researcher of diseases. infectious at Hacettepe University in Ankara and coordinator of the CoronaVac study in Turkey. But this vaccine, adds the expert, is still valuable because it will prevent the most serious cases of the disease.

The delays in communicating the results of the Brazilian trial, therefore, have led Turkey to rely on the first efficacy data vaccine from your clinical trial. At the end of December, the experimentation carried out in this country had shown that CoronaVac was 91.25% effective in preventing symptomatic disease based on 29 Covid-19 cases out of 1,322 volunteers. Indonesia, another country where trials for this vaccine are underway, also authorized CoronaVac for emergency use and started its national vaccination program in recent days. The results of their study, in this case, demonstrated a vaccine efficacy of 65.3% in preventing symptomatic infections based on 25 cases of Covid out of a total of 1,600 volunteers. "Given the large population of Indonesia, many people could benefit from the vaccine even with 65% efficacy," explains Jarir At Thobari, of Gadjah Mada University, Indonesia.

Experts, however, reiterate that the mixed results shouldn't come as a surprise when it comes to a less effective vaccine tested in a relatively small number of people. "If a vaccine has really high efficacy, it doesn't take many numbers to get a clear picture. But when that's not the case, then you really need much bigger numbers to get a better view of what's going on, ”explains Hilda Bastian, a researcher at Bond University in Australia. Researchers from the Butantan Institute, however, speculate that the lower efficacy of CoronaVac compared to other vaccines may be due to the fact that the two doses were administered two weeks apart, thus not leaving enough time for volunteers to reach the peak immunity. Based on the data reported so far, however, the vaccine appears to be safe, with only a few people experiencing mild symptoms, such as headaches.

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