The members of the independent research group OCTA on Monday, Aug. 9, cited that the pandemic model they are using has been useful in providing coronavirus disease (COVID-19) trends in the country.
OCTA Research fellow Dr. Guido David said the reproduction number is the primary indicator used to study COVID trends.
He also cited that the positivity rate, which is the number of people who test positive given the testing, is also a strong supporting indicator.
OCTA also studies health care utilization to measure the impact of the pandemic.
"When the reproduction number starts increasing, we need major interventions to stop the cases from swelling or to slow down or decrease the reproduction number," David said in an online forum organized by the Philippine-American Academy of Science & Engineering (PAASE).
"Some argue that we should not be using the reproduction number but it actually is the indicator, it is the variable that is used worldwide to project the number of cases and determine trends. Why is it the primary indicator? Basically, it measures the rate of infection. Especially, it measures the speed or the strength of the pandemic. That's why this number is very important. It's like a temperature. If it's high, it means that things are getting bad. If it's low, things are improving," he explained.
David also pointed out that the reproduction number is estimated based on the number of new cases using the data from the Department of Health (DOH).
He said that the DOH produces three data--the report date or the date the case was reported; specimen date or the date the specimen was obtained; and onset date or the date of onset of disease.
He cited as an example data from July 1 to Aug. 8, 2021, to explain that these are correlated.
"This is the picture if we align the report date with the specimen date two days ago and onset date three days ago. We can see that there is a fairly high level of correlation," he said. "If we use the report date, it's very highly related with the onset date from three days ago. It's not 14 days ago as some critics are claiming that our data is wrong and unreliable. In fact, it's highly reliable as long as we understand that what we were looking at yesterday is minus three days, four days."
"Is that a big error or problem? No. Because firstly we understand that what we are looking at is really three to four days old, and that's fine. That's not a big change in our projections," he added.
David further explained that case reports may be used to calculate the reproduction number even given the three-day lag.
In the event of a surge, it serves as a lower estimate of the true reproduction number, he added.
For his part, OCTA fellow and biologist Fr. Nicanor Austriaco said the group's pandemic model is "useful," citing OCTA's forecast scenarios for Metro Manila's hospitals that they would exceed critical capacity by the middle to end of August.
Based on the projections made on July 28, 2021, Austriaco said that around 4,500-4,600 total COVID-19 beds will be occupied in Metro Manila.
"Apparently, despite those who called us alarmists, the Delta surge is worse than our projections had anticipated. Once again, it looks like our model, though crude, is making useful forecasts," Austriaco said.
"I am grateful that the DOH FASSTER modelers have corroborated our findings that the Delta surge would overwhelm our hospitals. We are working together as Filipino scientists and modelers to serve our country against a common enemy, which is COVID-19," he added.
Austriaco emphasized that models used by OCTA and DOH are both useful.
"Some have asked me if our model is better or worse than the DOH model. This is the wrong question to ask. Instead, we have to ask: Are our models useful?" he pointed out.