FAST FACTS: What you need to know about the Sinovac vaccine

ABS-CBN News

Posted at Feb 28 2021 07:28 PM | Updated as of Mar 01 2021 12:12 AM

Boxes of Sinovac Biotech's CoronaVac vaccine against the coronavirus disease (COVID-19) arrive in a Chinese military aircraft at Villamor Air Base in Pasay, Metro Manila, Philippines, February 28, 2021. Eloisa Lopez, Reuters

MANILA — The Philippines will be starting its vaccination program against COVID-19 with jabs from Chinese pharmaceutical firm Sinovac, which arrived Sunday. 

Here’s what you need to know about Sinovac vaccine:

‘Varying’ efficacy rate

Researchers in Turkey said it is 91.25 percent effective. Turkish trials had included over 7,000 volunteers, but the efficacy result was based on data from 1,322 people.

Indonesia said the vaccine is 65 percent effective based on trials involving some 1,600 people.

Researchers in Brazil said it was 50.4 effective at preventing symptomatic infections, barely enough for regulatory approval and below the 78 effective announced a week earlier.

Brazil has run the biggest trials so far with around 13,000 participants.

The Sinovac vaccine however appeared to be safe in a late-stage clinical trial in Brazil, as preliminary results have shown in October. 

Trial size, patient criteria, duration of post-vaccination observation, target groups, prevalence of the virus in each site are among the factors that could impact efficacy, experts said.

More rampant infections in Brazil than in other trial sites and its study design to focus on medical workers could have led to more mild infections in trials, thus lowering efficacy data, a person familiar with the matter said, according to a Reuters report.

Medical workers could be more alert to mild symptoms and report those more proactively than general public, which Sinovac suspects may be among the reasons behind the less robust 50 percent reading, the person said.

Fake positive results delivered by high-sensitivity COVID-19 tests may have also worsened the reading, the person added.

Sinovac is also not the only vaccine with varying success rates. 

AstraZeneca's vaccine showed 62 percent efficacy when two full doses were administered to adult participants of all age groups, but it rose to 90 percent in a sub-group of smaller number of participants not older than 55 who were given a half-dose followed by a full dose booster.

China’s state-backed Sinopharm showed 79.34 percent efficacy, lower than 86 percent announced by the United Arab Emirates based on preliminary data from trials there.

Number of doses and allocation

At least 600,000 Beijing-donated Sinovac doses are expected to reach Philippine shores. 

Authorities are still assessing which of the priority sectors in the country's vaccination program will receive the 500,000 doses of Sinovac's vaccine, after the country's Food and Drug Administration noted that the product yielded a low efficacy rate of 50.4 percent when used on health care workers exposed to COVID-19 during its trial.

At least 100,000 doses, meanwhile, are specifically allotted to the Department of National Defense.

Workers in hazmat suits disinfect a box containing Sinovac Biotech's CoronaVac vaccine against the coronavirus disease (COVID-19) after unloading it from a Chinese military aircraft at Villamor Air Base, Pasay, Metro Manila, Philippines, February 28, 2021. Eloisa Lopez, Reuters

Clinical trials with PH

As early as July, the Philippines was in talks to join a Beijing-based biotech firm's human trial for the said vaccine.

Sinovac said in April that its novel coronavirus vaccine "largely protected" monkeys from infection during an animal trial. 

Five hospitals handled the clinical trials: Philippine General Hospital, the Research Institute for Tropical Medicine, Manila Doctors Hospital, San Lazaro Hospital, and Vicente Sotto Memorial Medical Center.

The Department of Science and Technology (DOST) said that if the Philippines wants to be among the first to access vaccines for COVID-19, it would help if it participates in clinical trials.

Assessing its recipients

Experts say it is difficult to interpret the efficacy results as the full datasets are not out.

“This highlights the problem of issuing data by press release rather than publication in a peer-reviewed journal,” Lawrence Young, a virologist and professor at Britain’s University of Warwick, said.

Paul Hunter, professor in Medicine at University of East Anglia, noted the dosage interval of two weeks was very short and may have contributed to the less-than-impressive efficacy.

In the Philippines, experts have varying answers on who can receive the vaccine.

The Food and Drug Administration granted its emergency use authorization in late February but noted that it was not a recommended brand in inoculating health workers, which is the government's priority sector.

A health expert also said the Sinovac vaccine works best for the general public with moderate-risk exposure to COVID-19.

The general manager of Sinovac Biotech, however, defended their COVID-19 vaccine and said that it can be used for health workers and the elderly.

- With a report from Reuters

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