MANILA - Persons who have contracted COVID-19 still need vaccines and booster shots as various variants of concerns emerge, experts said Tuesday.

Antibodies from vaccination and infection wane over time, according to Dr. Liza Gonzales, associate dean at the UP Manila College of medicine and member of government's vaccine expert panel (VEP).

"The vaccination of individuals previously exposed to the virus boosts the existing immune response," she told reporters.

"In general the neutralizing antibody titers we have compared to the Wuhan strain is generically lower against the variants. Vaccination would result in neutralizing antibodies that are still active against the variants."

For individuals vaccinated with Russia's Sputnik V vaccine, antibodies begin to wane 60 days after inoculation but it remains detectable even after 90 days, said Gonzales.

These are maintained for at least 4 months and showed a "reduction of VOC (variant of concern) escape over time of vaccination," according to UP scientist Dr. Derick Sumalapao, citing a study conducted in Argentina.

"There was an improved antibody cross-neutralizing ability to circulating variants of concern specifically Beta, Gamma, and Delta was observed over the time of vaccination," he said.

Gonzales also cited a study which found that the decrease in neutralizing antibodies, or those that kill pathogens, against omicron in persons inoculated with Sputnik V was lower than individuals jabbed with Pfizer's vaccine.

• In preliminary study, Sputnik V shows higher omicron-antibody levels than Pfizer

Omicron-specific neutralizing antibodies were found in 74.2 percent of those vaccinated with Sputnik V and in 56.9 percent of those inoculated with Pfizer, according to Gonzales.

"The vaccines given as a booster will enhance your protection against the variants. It's difficult to say if Sputnik has an advantage over Pfizer or Moderna. They are all effective if you give them against a variant of concern at this point," she said.

The public is urged to get vaccinated against COVID-19 to prevent more transmissions which can lead to more mutation of the coronavirus.

"As long as this virus is transmitting, there will always be variants that will be emerging," Gonzales said.

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