Sinovac vaccine effective against viral variants in Brazil; effectiveness increases if the injection interval is longer than 21 days

Indigenous Guarani chief Jurema Nunes receives a vaccine against CoronaVac during a COVID-19 vaccination campaign in Marica, Brazil on January 20.  Photo: VCG

Indigenous Guarani chief Jurema Nunes receives a vaccine against CoronaVac during a COVID-19 vaccination campaign in Marica, Brazil on January 20. Photo: VCG

China’s Sinovac COVID-19 vaccine is 50.7% effective and has been shown to be effective against the variants known as P1 and P2 which are prevalent in Brazil, according to the latest data. In addition, the efficacy rate of the Sinovac vaccine can climb to 62.3% with an interval of more than 21 days between doses instead of 14 days.

The results appear in the latest report released Sunday by the Butantan public institute in Sao Paulo, which tested and produced Sinovac’s inactivated COVID-19 vaccine called CoronaVac.

The report published specific and comprehensive data on advanced stage trials in Brazil. This is the most detailed statistical report on a Chinese COVID-19 vaccine.

The primary efficacy against symptomatic COVID-19 is 50.7 percent. The vaccine is 83.7% effective in preventing cases requiring assistance, up from 78% according to data released in January. It is 100% effective against moderate and severe cases in the randomized, double-blind, placebo-controlled phase III clinical trial involving 12,396 participants, statistics showed.

The efficacy rates revealed in this report are slightly higher than those reported in early January, due to tracking changes in clinical data and the different criteria used to define cases of infection, spokesperson Liu Peicheng of Sinovac to the Global Times.

The researchers found that longer intervals between two jabs can provide higher efficiency, in line with observations from many Chinese medical researchers who recommend a longer interval to maximize the level of immune antibodies.

All six severe cases of COVID-19 occurred in the placebo group. There were 67 serious adverse events reported by 64 participants and all were determined to be unrelated to vaccination, including two fatal cases, he says.

The final results and relevant statistics are identical to those that received conditional approval from the Chinese drug regulator in February.

“This is the most detailed phase III study of a COVID-19 vaccine made in China to date. Overall, it demonstrates that CoronaVac has a good safety profile, and is effective and protective against symptomatic infections, “said Zhuang Shilihe, a Guangzhou-based physician who closely monitors COVID-19 vaccines, told the Global Times on Monday, noting that its effectiveness can be further optimized by lengthening the interval between doses.

But undeniably, compared to inactivated vaccines, the efficacy of mRNA vaccines is higher, if not much higher than some common vaccines on the market, which has raised expectations, Zhuang suggested.

“But that doesn’t mean inactivated vaccines aren’t qualified. Take influenza vaccines, for example – actual efficacy rates in many countries are between 40 and 50 percent, but this type of vaccine is still officially recognized and widely accepted. “

Sinovac has also submitted detailed data to the WHO and drug regulators in countries or regions that use CoronaVac, and relevant authorities will review those detailed figures before making approval decisions, the Sinovac Global Times has learned.

CoronaVac has been approved for emergency use in various countries, such as Pakistan and Panama.

Some media recently blamed CoronaVac’s effectiveness rates for high infections in Chile, citing a University of Chile study that claimed that the effectiveness after the first injection of CoronaVac was only three percent.

But a source familiar with the matter told the Global Times on Sunday that the university’s report is not “comprehensive and authoritative” and is based on “very limited” open data.

“The data was just an ‘exercise’ carried out by a research team at the university, based on public data. It is very limited, not even close to writing an article,” the said. source.

The official and global data of the CoronaVac vaccine deployment will be released next week by the Chilean Ministry of Health, Sinovac’s Global Times learned on Sunday.