A woman gets a booster shot at an elementary school in Marikina City, Nov. 25, 2021. — PHILIPPINE STAR/ MICHAEL VARCAS

WHILE the government began rolling out the second booster against coronavirus disease 2019 (COVID-19) this April, only about a fifth of fully vaccinated Filipinos have had their first booster, prompting doctors to remind the public that a third dose is needed to maintain protection.

A booster dose, regardless of the brand, restores protection against serious COVID-19 outcomes, according to a review of 79 real-world studies on VIEW-hub, an interactive platform for data visualization on vaccine use and impact by the Johns Hopkins Bloomberg School of Public Health and IVAC (International Vaccine Access Center).

Conducted by 18 Southeast Asian infectious disease experts, the review posted April 25 included outcomes for both mRNA vaccines and the AstraZeneca vaccine.

“We live in an Omicron world, and two doses is not optimal protection against [the coronavirus variant],” said Dr. Bruce Mungall, Asia area medical director of vaccines and infectious diseases at AstraZeneca, during an April 27 event organized by the multinational pharmaceutical company and the Philippine College of Physicians (PCP).

“A booster dose is important for protection against Omicron,” he added.

As of May 1, only 19.8% of fully vaccinated Filipinos (or 13,487,275 of 67,911,471) have had their first booster.

Data from the UK shows that vaccine-induced protection against symptomatic COVID-19 infection wanes over time, Dr. Mungall said.

“For [the] Delta [variant], there is a sustained effectiveness over time — but effectiveness against Omicron drops 30% after six months of the second dose,” he added.

The same UK data shows that when individuals are given either an AstraZeneca or Pfizer primary series plus an mRNA booster, there is an immediate restoration of protection (in the 80%–90% effectiveness range) against hospitalization.

Dr. Mungall said another study had similar results: “If AstraZeneca is given as a booster, the effectiveness against overall infection goes up about 60%.”

Data from the review will help take the Philippines into the endemic phase of COVID-19, according to Dr. Ma. Encarnita C. Blanco-Limpin, PCP president.

“Anyone vaccinated with either the viral vector or mRNA vaccines can be assured that they will be highly protected from death or hospitalization due to the virus,” she said.

“The most important part of this expert review is that we can’t rely on measuring antibodies as a measure of [a vaccine’s] effectiveness against complications,” added Dr. Rontgene M. Solante, a vaccine expert with the Department of Health and one of the authors of the Southeast Asia review.

Antibodies for the virus that causes COVID-19 are expected to wane over time.   

“Even with waning antibodies, the [vaccine’s] protection is still there against severe COVID-19 and severe hospitalizations,” Dr. Solante said. “That’s why we discourage people from taking antibody tests. What’s more important is that you are protected against severe forms of complications.” — Patricia B. Mirasol