Sinovac vaccine may have ‘different effectiveness’ – expert

By Joseph B.A. Marzan

 

An Ilonggo infectious diseases specialist on Monday said that the vaccine against the coronavirus disease 2019 (COVID-19) made by Chinese company Sinovac Biotech may be more effective than what is being presented.

The Beijing-based biopharmaceutical company conducted its clinical trials on CoronaVac earlier this year when the Chinese government approved such trials for the said vaccine.

The trials were conducted in Brazil, Chile, Indonesia, and Turkey.

A Reuters report stated that Brazilian scientists on Dec. 23 report that the vaccine had an efficacy of “more than 50 percent” during clinical trials with 13,000 volunteers.

The full report by the scientists was not released to the public as requested by Sinovac themselves, casting doubt over transparency on its effectiveness in preventing the disease.

Turkish officials, however, on Dec. 24 said trials with 29 volunteers showed an efficacy rate of 91.25 percent.

National government officials in the Philippines have been leaning towards getting CoronaVac as the first vaccine to be administered some time in 2021.

This raised questions as Western companies such as Pfizer and Moderna, whose vaccines have shown up to 95 percent efficacy rate, were not given preference.

Pfizer and Moderna have already started to provide their vaccines to the United States and the United Kingdom, with deliveries being made to Canada and Singapore.

The Philippine Council on Health Research and Development’s executive director, Jaime Montoya, said that the rate of CoronaVac was “acceptable” as it was within the World Health Organization’s vaccine threshold of a 50 percent efficacy rate.

Despite these, the government continues to be criticized by opposition politicians and netizens over its preference of a less-effective but more-expensive vaccine.

Dr. Ella Mae Divinagracia, Infectious Disease Specialist at St. Paul’s Hospital Iloilo explained the difference between the “efficacy” and “effectiveness” of the vaccine in an interview with Aksyon Radyo Iloilo.

Efficacy refers to the rate of the effect of the vaccine during controlled clinical trials, while effectiveness refers to the extent of the performance of the vaccine once they are administered to the general population, according to Divinagracia.

She added that the effectiveness continues to be assessed even after they have been administered to the public.

 

“When we say efficacy, [it means] the effect of the vaccine during the clinical trial conducted on that particular vaccine, whereas effectiveness is the extent of the performance of the vaccine in real life. We balance the benefits and risks of the program, not just the potency of the vaccine. It assesses the overall effect of the vaccine in the population, which includes herd effects, or the number of people who have been immunized,” said Divinagracia in the radio interview.

 

She suggested that the rates between efficacy and effectiveness may not be the same, taking several factors into consideration, some of which being the patients’ bodies, and the area where it is administered.

 

“[In Turkey], where this vaccine was given, they have [91] percent, meaning that there is progress as this is being used. What are the factors? Of course, we need to look at the host, the patient, the person who was given the vaccine. In every disease, every infection, there is a factor of the host, or the person, who plays an important role, the physical makeup of the person. Some people’s immune systems are strong enough to mount a desired immune response. There are those which are weaker,” she added.

 

She also said that the reason why the effectiveness is continuously being assessed even after public distribution of vaccines is because it “may still rise and fall”.

 

“When it arrives to the general population, in real life, it can be altered. It can rise and fall. That is why evaluation on the effectivity of the vaccine is continuous. It is being observed even if it is already being used, it is still being assessed. At least when there are more, our aim is to provide to a great number of the population and develop herd immunity,” she said.

 

She remarked that the Department of Health (DOH) has a “big role” in ensuring that the vaccines are safe for the people to use, and to encourage them to take the vaccines.

 

“The [DOH] really has a huge role to explain to the population on the role, usefulness, and effectivity of these vaccines. Of course, it is part of the Department of Health’s mandate to assure the people that this is safe, once it becomes available,” she said.