Various questions have emerged regarding the low efficacy of CoronaVac, the Covid-19 vaccine produced by Sinovac Biotech China, in Phase III of the clinical trials in Indonesia compared to in other countries.
By
Atika Walujani Moedjiono
·4 minutes read
Various questions have emerged regarding the low efficacy of CoronaVac, the Covid-19 vaccine produced by Sinovac Biotech China, in Phase III of the clinical trials in Indonesia compared to in other countries. It was said that the efficacy of CoronaVac in Brazil was 78 percent, in Turkey 91.25 percent, while in Indonesia it was 65.3 percent with 99.23 percent immunogenicity up to three months after injection.
Efficacy, according to the website of the Global Alliance for Vaccines and Immunization (GAVI), is the extent to which the vaccine prevents disease, and if possible also prevents transmission, under ideal and controlled conditions. This is done by comparing the vaccinated group with the placebo group (receiving substances that have no therapeutic value). A vaccine with 65.3 percent efficacy in clinical trials meant a 65.3 percent reduction in cases of illness in the vaccinated group compared to other groups, which are neither vaccinated nor given placebo.
Meanwhile, immunogenicity is the ability of foreign substances, such as antigens or vaccines, to trigger an immune response in humans or animals.
Measuring efficacy
The difference in efficacy (between countries), according to the chairperson of the Covid-19 task force for the Indonesian Doctors Association Prof. Zubairi Djoerban, on Tuesday (12/1/2021), is because efficacy is determined by a number of factors, such as the background of the volunteer groups during clinical trials and the epidemiology of the clinical trial area.
In Brazil, volunteer groups are health workers who face daily high exposure to the SARS-CoV-2 virus that causes Covid-19. When compared with the placebo group, the decrease in Covid-19 cases in the vaccinated group was quite high.
Volunteers in Turkey are health workers and the general public. Meanwhile in Indonesia, all volunteers are the general public, whose risk of infection is relatively low compared to health workers. If the placebo groups are disciplined in adhering to health protocols, the drop in Covid-19 cases between the vaccinated and placebo groups would not have been much different. Ultimately, the vaccine\'s efficacy (in Indonesia) was measured to be lower than the vaccine’s efficacy during trials involving volunteers from groups of health workers, such as in Brazil and Turkey.
Regarding epidemiology, cases in other countries are much higher. As of 11 January, Brazil recorded 8,133,833 positive cases and in Turkey 2,338,476 cases. Meanwhile, Indonesia has 846,765 cases. "In countries with more cases, the assessment of the efficacy of vaccines can be better because they can reduce cases in a larger number," said Zubairi.
A 65.3 percent efficacy does not mean that the remaining 34.7 percent is unprotected. By getting vaccinated, even though they are still infected, the disease is not severe. It can be without significant symptoms. Moreover, (things will be better if) the immunogenicity of the vaccine is 99.23 percent. Even if infected, the ability of antibodies against the virus is very high.
How about effectiveness? Efficacy is measured under ideal and controlled conditions while effectiveness is a measurement of a vaccine performance in the real world. Vaccines with an efficacy of 90 percent may not have 90 percent effectiveness once they have been applied to the wider public.
Various factors -- such as the medicines someone is consuming, chronic disease someone is having, age, how vaccines are stored and injection procedures – would determine the effectiveness of vaccines in preventing the disease. Surveillance data are essential to understand the effectiveness, for example when people get vaccinated and what is the vaccination coverage in a country. If the vaccine is effective, any persisting case would occur most possibly on individuals who are not vaccinated.
Although the efficacy of a vaccine, which is produced from attenuated viruses, such as CoronaVac, is lower than the efficacy of viruses made from mRNA, such as Pfizer-BioNTech or Moderna products, according to the Health Ministry director for prevention and control of direct infectious disease, Siti Nadia Tarmizi, the side effects are also lower. So far the only side effects of CoronaVac that have been monitored are pain and swelling at the injection site and a light fever.
This articles was translated by Kurniawan H. Siswoko.