The Philippines received an additional one million doses of Sinovac vaccines against the coronavirus disease (COVID-19) on Monday morning, June 28, amid mounting calls to stop the procurement of the Chinese brand and start prioritizing Western brands which are supposedly more effective against the Delta variant.

A Cebu Pacific plane (flight 5J671) brought the CoronaVac vaccines made by Sinovac Biotech from Beijing to Terminal 2 of the Ninoy Aquino International Airport (NAIA) in Pasay City around 7:30 a.m.

Vaccine czar Carlito Galvez Jr. and Health Sec. Francisco Duque III welcomed the arrival of the vaccines. The new delivery brought the country's total supply to 17,455,470 doses--12 million of these doses are Sinovac jabs.

Galvez underscored the importance of the steady delivery of the Sinovac jabs to ensure the continuous implementation of the national immunization program.

This month alone, Sinovac has shipped a total of 6.5 million doses -- the most among the five companies that are currently supplying COVID-19 vaccines in the country. Aside from Sinovac, other brands that are available include Pfizer, AstraZeneca, Sputnik V, and Moderna.

However, Senator Franklin Drilon urged the government to veer away from procuring Sinovac shots and start prioritizing the purchase of more effective vaccines particularly Pfizer from the United States.

"Maybe we should start a policy which would ultimately use Pfizer as the primary vaccine brand because based on studies, Pfizer is more effective than Sinovac)," the lawmaker said in a radio interview over DWIZ last Saturday.

In response, Galvez said Sinovac vaccine remains efficacious in preventing severe COVID-19 cases which often lead to death and hospitalization.

The Department of Health (DOH) said Sinovac has an efficacy rate if 65 to 91 percent based on clinical trials in Brazil, Indonesia, and Turkey as of March 2021. Meanwhile, Pfizer has a higher efficacy rate of 95 percent.

As for the more transmissible Delta variant, which is becoming the globally dominant variant of coronavirus, Pfizer was proven to be 79 percent effective in providing protection two weeks after getting the second dose, DOH Undersecretary Maria Rosario Vergeire said on June 21, citing clinical trials conducted in the United Kingdom.

Meanwhile, health experts have yet to determine how effective Sinovac is against the Delta variant as there are currently no available data on this.

Still, Galvez maintained that the government will pursue its procurement of 25 million doses of Sinovac jabs as it banked on the diligence of the Chinese manufacturer in delivering the vaccines on time as compared to other brands.

"Nakita natin wala namang basis ang comment, wala namang clinical data na ang Sinovac ay hndi effective sa variants (We have seen that comment has no basis as there is no clinical data showing that Sinovac is not effective against the variants)," Galvez said.

"Ang kanyang efficacy in terms of preventing death and severe cases ay nasa 94 to 95 so ito ang tinitignan natin. Ang Sinovac, 28 countries ang tumatanggap and also ito ang pinakasteady supply sa ngayon. Sa lahat ng manufacturers, siya ang very diligent at on time (Its efficacy in terms of preventing death and severe cases is around 94 to 95 so this is what we are looking at. Sinovac is being used in 28 countries and it also provides the most steady supply right now. Among all manufacturers, it is very diligent and on time)," the vaccine czar added.

Meanwhile, the government signed last week the supply agreement for the procurement of 40 million doses of Pfizer, the biggest vaccine procurement it made this year. The delivery of the Pfizer vaccines will start in August.