The effective reproduction number (Rt) of Covid-19 cases in the country, now at 0.83, continues to drop, an infectious disease expert said Wednesday.

In a Facebook post, infectious diseases expert Dr. Edsel Salvaña, who is also a member of the Department of Health (DOH) Technical Advisory Group, said the less than one Rt of infections nationwide has a 90 percent confidence interval, from 0.73 to 0.93.

The Rt, the virus’ actual transmission rate at a given time, refers to the growth or decrease in cases.

“That upper limit of 0.93 is very important, as it shows that the Rt is almost definitely less than 1 even if we take a very conservative view of the data. As always, these refer to cases that were most likely infected 2 weeks ago and so it doesn’t necessarily predict what is currently happening in real time,” Salvaña said.

With the downward trend, the positivity rate and healthcare utilization rates are also going down.

“However, Delta and the next variants are still lurking and it is not yet time to relax. Keep those masks on and let’s get everyone vaccinated,” Salvaña said.

On Tuesday, the DOH reported 9,055 new reported cases – much lower than the over 20,000 infections logged last week.

“Some may also have noticed an increase in severe and critical among active cases. This is due to the fact that tagged recoveries from asymptomatic and mild are done 10 days from positive/start of symptoms respectively while it takes 21 days for severe/critical to be tagged as recovered,” Salvana said.

He said a bigger proportion of severe and critical cases would be left, as asymptomatic or mild cases are tagged as recovered.

“This should go down naturally in 1 to 2 weeks as the recoveries (or also unfortunately, deaths) from severe and critical are tagged,” he said.

All Covid-19 vaccines effective

Salvaña reiterated that the efficacy of Covid-19 vaccines “do not stop working at six months”.

Citing latest data from the Philippine Food and Drug Administration, he said there was no evidence showing the waning in clinical efficacy over time for any of the Covid-19 vaccines.

“Antibodies go up and down, but T-cells are much longer-lived. Even Dr. Nina Gloriani, who was horribly misquoted by media as saying some vaccines only last six months, eight months or one year has already set the record straight,” Salvaña said.

He added that Gloriani was referring to antibody levels which are not the only correlates of protection.

Health experts have said all available vaccines continue to protect the population against severe symptoms of Covid-19 and even death.

Salvaña also said booster shots may benefit senior citizens, individuals with comorbidities, healthcare workers but these have yet to be scientifically proven.

“We need to prioritize people who have no protection at this time. Let’s focus and get as many people vaccinated with whatever brand as soon possible and that will give us much more protection as a society than giving unproven booster,” he said.