The Food and Drug Administration (FDA) clarified on Thursday that the AstraZeneca vaccines may still be used as a booster shot for people who received the same brand in their primary series.

This comes after Dr. Edsel Salvana on Wednesday urged AstraZeneca vaccine recipients to pick a different brand for their booster shots, theorizing that using the same one could lead to a possible decrease of efficacy.

"It's a theoretical possibility of decreased efficacy," he said during a Town Hall meeting on COVID-19 boosters.

But FDA Director-General Eric Domingo told DZRH in an interview that the AstraZeneca jabs are still a "viable option" for a homologous booster.

On Salvana's word of caution, Domingo said it was just the expert's opinion.

"I think 'yun 'yung personal opinion niya, nakita ko rin naman, sabi niya it's theoretical parang sa isip niya, 'yun yung possible na nangyari," he told DZRH in an interview.

(I think that’s his personal opinion. I saw it too and he said it’s theoretical, like in his mind, that could possibly happen.)

"Sa data na nakita ng experts natin show na meron siyang additional value kapag bumababa na yung antibodies nga dun sa pasyente na nakatangaap ng AstraZeneca dati," he said.

(Data from our experts showed that there is additional value once antibodies go down in patients who received AstraZeneca vaccines.)

"So it's still a viable option, pwede siyang homologous vaccine," he said.

"Of course pwede rin naman gumamit ng heterologous or iba 'yung booster shot from the primary series," he said.

(Of course, they may still go heterologous, or a different booster shot from the primary series.)

According to the Department of Health, for heterologous boosters, the following combinations can be used:

For AstraZeneca: Pfizer of Moderna

For Gamaleya Sputnik V: AstraZeneca, Pfizer, or a Moderna

For Ad26.COV2.s (Janssen): AstraZeneca, Pfizer, or Moderna

For Moderna: AstraZeneca or Pfizer

The government has begun rolling out booster shots for healthcare workers since Wednesday.