Herd immunity in the country may be "out of reach" due to the attributes of the coronavirus variants, a health expert said Monday, Sept. 13.

"Now we know that herd immunity will be out of reach based on several factors. First, vaccines may not be transmission-blocking," said Epidemiologist and Senior Technical Adviser of EpiMetrics Dr. John Wong in a virtual town hall meeting.

While vaccines may not prevent infections, these are still very effective in preventing deaths and hospitalizations, he noted.

"Second, there are new variants that are more transmissible and are vaccines resistant. Alpha is more transmissible, Beta is more vaccine resistant, and Delta is both," Wong said.

He said another factor is that vaccination rollout in the country is uneven.

Wong noted that so far the current vaccine supply available is only 28 million.

"Although we have prioritized those at risks for death and hospitalizations -- frontline health workers, elderly, persons with co-morbidities -- we don't have enough supply for everyone," he said.

The country is also now seeing waning vaccine immunity among the elderly and people with comorbidities, the expert said.

He then urged the government to vaccinate people above 50 years old to prevent 80 percent of deaths.

Aside from this, Wong said the behavior of the people will also likely to change as soon as the economy opens up again and people have to return to work with less restrictions.

Wong also listed down five criteria to consider in returning to work: the level of community transmission, health system capacity, vaccination coverage, capacity for early detection of cases, and population at risk for severe outcomes.

Over 16 million individuals in the Philippines have already been fully vaccinated against COVID-19.