Using a different brand of vaccine against coronavirus disease as a second dose is not harmful to the recipient, but the efficacy may not be the same, a health expert said.

Lulu Bravo, executive director of the Philippine Foundation for Vaccination and chairperson of the National Adverse Events Following Immunization Committee, made the statement amid the tight supply of vaccines abroad.

"Actually, it remains to be investigated. But there is no harm," she said in the "Laging Handa" public briefing on Saturday when asked of the possible initial response of the immune system of a person who receives two different brands of vaccines.

In general, she noted that this scenario happened before in other types of vaccines, such as those administered to children, not only for COVID-19.

"There's no company yet which is conducting a study that it's vaccine will be mixed with others, that is never done before. But with the epidemic...there are already some companies (doing it), she said.

''Even Chinese companies and other firms are really thinking that when there is insufficient vaccine and there's no available vaccine for the second dose, it's really possible to use other brand of vaccine and see if the efficacy is the same," she explained.

"It won't be harmful but the efficacy may change," Bravo added.

The efficacy can be high or low or even the same, she said.

The government has acknowledged it has found difficulty in immediately securing certain brands of COVID-19 vaccines for the Filipinos.

Authorities have used all the AstraZeneca vaccine doses, which were delivered in the country under the World Health Orgaization-led COVAX facility, as first shot to healthcare workers and senior citizens.

The Philippines has yet to receive more doses of UK brand vaccine to be used as a second dose. Celerina Monte/DMS