MANILA - The Philippines should vaccinate its entire population against COVID-19 as the more virulent Delta variant continues to spread around the world, the head of the country's vaccine expert panel said Thursday.

Several studies showed that while existing COVID-19 vaccines still protect individuals from severe infection, their efficacies against the Delta variant have been reduced, said Dr. Nina Gloriani.

"I think we need to do higher and faster vaccinations... because this Delta variant is a real concern," she said in an online press conference.

"One hundred percent, lahat (everyone)," she added.

Thirteen out of 20 individuals jabbed with Sinovac or 65 percent of samples "showed decreased neutralizing activity against the Delta variant," Gloriani said, citing a study published on July 9, 2021.

Despite getting a Sinovac jab, the Delta variant reduced antibodies in these patients by "2.5-fold," she said.

"Two doses of CoronaVac (Sinovac) induced good immunogenicity, although neutralizing antibody levels declined... after 6 months," she said.

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AstraZeneca's efficacy was also reduced against the Delta variant, Gloriani said, noting that antibodies from the vaccine dropped by 5.11 against the more virulent strain first detected in India.

A separate study showed that "2 doses of AstraZeneca only had 60 percent protection," while Pfizer's COVID-19 vaccine "only had 79 percent against the Delta variant," she said.

"They (Pfizer) are now saying nag-decline, so we really have to look at those specific data," she said.

A study from Argentina showed neutralizing antibodies from Sputnik V were also reduced by 2.5-fold against the Delta variant, Gloriani said.

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Moderna's Geometric mean titre (GMT) or the average antibody measurement for a group of subjects dropped to 350 against the Delta variant, a steep decline from its 1,062 GMT against the original COVID-19 strain, she said.

"For us to get better immunity, siguro pataasin natin 'yung target [vaccination] natin," said Dr. Rontgene Solante, an infectious disease expert who is also part of the Philippines vaccine expert panel.

"When you have a variant that is highly transmissible, and your protection is 65-70 percent, it is not enough. You need to vaccinate everyone," he said.

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Solante said vaccinating the entire population is also safer for the Philippines as the country does not "have a good grasp of what is the percentage of Delta in daily cases."

"We need to look at the trend of the Delta variant... If it's 50-60 percent of daily cases, that is really something," he said.

Despite these recommendations, the vaccine experts noted that more studies have to be done especially in the inoculation of young children against COVID-19.

"'Yung pediatric, mababa pa naman yung kaso, though they can be drivers of transmission," Solante said.

"'Yung bakuna ng mga bata, wala pa tayong magandang study... Remember, these are children, high risk din ito for adverse reactions," he said.

The vaccine expert panel is also reviewing if there is a need to recommend booster shots for "special populations," Gloriani said.

The special population includes HIV and cancer patients, those taking immunosuppressive drugs, and those with chronic kidney diseases, Solante said.

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Gloriani warned the public against taking booster shots without recommendations from experts, noting that its efficacy would vary on how long it was administered after the first 2 doses of the COVID-19 vaccines.

"If you want booster doses, it should not be given too early," she said.

"It was found that giving booster doses too early like 28 days after the second dose, induced a much lower antibody level. That's only one-third, compared with a third dose given 6 or more months after a second dose," she said.

As of July 28, the Philippines has fully vaccinated 7.2 million people, or about 10 percent of the maximum target number for the country to attain herd immunity against the disease.

Some 11.4 million first doses of different COVID-19 vaccine brands have also been administered.

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Video from the Department of Health​