Experts reject proposal to shorten interval for Sinovac, AstraZeneca vaccines

Two members of the Vaccine Expert Panel (VEP) on Thursday rejected a proposal by an OCTA Research fellow to shorten the interval between the first and second dose of the Sinovac and AstraZeneca COVID-19 vaccines.

VEP head Dr. Nina Gloriani said data show that a longer interval between the two doses would lead to a higher level of antibodies against COVID-19.

“Hindi natin pwedeng bilisan [ang second dose] (We cannot hasten the second dose),” she said at a Palace briefing.

In a Health Department forum, VEP member Dr. Rontgene Solante also underscored that “we cannot afford shortening the interval from 28 to 14 days kasi nga medyo dehado tayo sa efficacy no’ng bakuna (because the vaccine efficacy will decrease).”

Health Secretary Francisco Duque III, meanwhile, told Super Radyo dzBB that the VEP has yet to make a recommendation to shorten the interval between the two doses.

“Meron pa ring taglay na proteksyon ‘yan pero hindi na siya kasing taas ng proteksyon na ibinibigay kapag sinunod mo ‘yung talagang 28 days, ‘yung original na protocol or indication para dito sa mga bakunang ito,” he said.

(That would still offer protection but not as high as what you’d get if you follow the 28 days or the original protocol or indication for the vaccines.)

The Philippines currently follows an interval of 28 days for Sinovac and 12 weeks for AstraZeneca.

The National Vaccination Operations Center, however, has recommended shortening the interval for AstraZeneca to just eight to 10 weeks. 

OCTA recommendation

At a forum on Wednesday, OCTA fellow Fr. Nicanor Austriaco suggested shortening the interval in order to fully vaccinate more people in Metro Manila amid the threat of the highly contagious Delta variant.

Austriaco suggested a 14-day interval for Sinovac and an eight-week interval for AstraZeneca.

The OCTA fellow said a Turkish trial published in the medical journal The Lancet “showed 83.5% protection” with the 14-day interval for Sinovac.

As for AstraZeneca, Austriaco said studies have shown that an eight-week interval “is still effective and responds to the Delta threat.”

Antibodies

The vaccine experts also stressed that a decrease in antibodies does not equate to reduced protection from COVID-19, after a Chinese study found that antibodies from the Sinovac jab fade after six months. 

Solante explained that the neutralization potency and breadth of antibodies “increases with time even if the quantity and level of the antibody decreases.”

“It’s quite difficult to just rely on an antibody titer to say that our immunity has waned because the other important part of the pathway of immunogenicity that we can be protected is to also look at the T cell immunity and the B cell memory,” he said. — RSJ, GMA News