A study is needed first before the government can push through with its plan to use AstraZeneca's COVID-19 vaccine as a second dose for Sputnik V, the head of the Food and Drug Administration (FDA) said Thursday.

Interviewed on Unang Balita, Director General Eric Domingo pointed out that the first component of Sputnik V is what is called "Sputnik Light," which reportedly can be given in a single dose.

"Ang alam natin yung first component ng Sputnik ay yun din yung tinatawag na Sputnik Light na baka maaaring single dose lamang [What we know is the first component of Sputnik is what is called Sputnik Light, which could be given in a single dose]," Domingo said.

"So lahat ng ito ay kinakailangang pag-aralan siguro muna bago maghalo ng mga bakuna [So all this must be studied first before we start mixing vaccines]," he added.

Domingo said Philippine vaccine experts are currently evaluating Sputnik Light and results may be out "within the next few days or next week."

On Wednesday, vaccine czar Carlito Galvez Jr. said AstraZeneca doses may be used as a second dose if the second component of Sputnik V fails to arrive in the Philippines.

Unlike other vaccine brands, the Russian-made Sputnik V has different components for its first and second dose.

Domingo said AstraZeneca and Sputnik V vaccines are "very similar."

"Sa ngayon ang alam nating puwedeng i-mix and match ay usually yung AstraZeneca plus yung mRNA vaccines, ang AstraZeneca at saka yung [Sputnik] ay very similar vaccines din," he said.

(What we know so far is we could probably mix and match AstraZeneca with other mRNA vaccines, and AstraZeneca and Sputnik are very similar vaccines.)

Domingo stressed that at present, the government only allows similar COVID-19 vaccine brands for first and second dose.

The Philippines is expecting 15,000 doses of Sputnik V's Component Number 2 or its second shot on Friday, August 13.

The latest shipment of Sputnik V vaccines was in July, wherein 37,800 doses were delivered from Russia.

Last month, health authorities discussed a plan to study vaccine mixing. COVID-19 vaccine brands included in the mix and match trials are AstraZeneca, Sinovac, Pfizer, Moderna, and Sputnik. --KBK, GMA News