The Coronavac vaccine was 86% effective in preventing deaths from Covid-19 in Chile, according to a study that followed the results of 10.2 million people in the country, published in the scientific journal New England Journal of Medicine on Wednesday (7).
For the doctor Juarez Cunha, president of the Brazilian Society of Immunizations (SBIm), the results are “encouraging” and show that the vaccine applied in two doses is safe and effective. “Chile’s real-life results are very good and are very similar to any other vaccine [contra Covid-19] that is being used,” he said. “The Chile study is very important because it is about a vaccine that we use a lot in Brazil and with a population with very similar characteristics.”
Among the 10.2 million people included in the study, 4.1 million were fully vaccinated with Coronavac and 542,000 were partially immunized. The survey tracked data from February 2 to May 1, 2021 to calculate effectiveness rates, which show how a vaccine works in “real life” with the mass vaccination campaign. The measure is different from the efficacy data, which are calculated in clinical studies done in controlled conditions and in specific groups.
Effectiveness of Coronavac for those vaccinated with two doses, after 14 days:
- 65.9% for Covid-19 prevention;
- 87.5% for the prevention of hospitalizations;
- 90.3% for the prevention of ICU admissions;
- 86.3% for the prevention of deaths.
These numbers mean that the risk of getting Covid-19 is 65.9% lower, and the risk of dying from the infection is 86.3% lower, for those who have been fully vaccinated with Coronavac. In other words, with the effectiveness shown for Coronavac, for every 100 people who would have died from the disease if there was no vaccination, there will be 13 deaths if everyone is vaccinated, detailed Rafael Araos, one of the study’s authors and Public Health advisor at the Ministry of Chile Health.
The lower rate of effectiveness for death than for admissions can be explained by the fact that there are people who died before being hospitalized, in a context where there is overcrowding of hospitals. “During the study period, ICUs in Chile were operating at 93.5% of their capacity, on average,” the authors point out. Because of this, estimates of protection for Covid-19-related deaths may be higher in the case of regular health care operation, the researchers say.
This scenario also happened in Brazil, says Cunha. “We certainly had people who died who did not enter the ICU. This possibility exists when there is a very high disease burden and a collapse of the health network, as Chile and Brazil had at certain times,” he explains.
The study showed that protection significantly increased after the second dose of the inactivated virus immunizer. Coronavac’s effectiveness rates for those vaccinated with the first dose, from 14 to 28 days after application, are as follows:
- 15.5% for Covid-19 prevention;
- 37.4% for the prevention of hospitalizations;
- 44.7% for the prevention of ICU admissions;
- 45.7% for the prevention of deaths.
The researchers also separately analyzed the subgroup of people over 60 years old. In this case, the protection also increased considerably after the application of the second dose of the immunizing agent.
Coronavac’s effectiveness among people with 60 years or more vaccinated with two doses, after 14 days:
- 66.6% for Covid-19 prevention;
- 85.3% for the prevention of hospitalizations;
- 89.2% for the prevention of ICU admissions;
- 86.5% for the prevention of deaths.
Coronavac’s effectiveness among people with 60 years or more vaccinated with one dose:
- 9.7% for Covid-19 prevention;
- 35% for the prevention of hospitalizations;
- 44.5% for the prevention of ICU admissions;
- 45.8% for the prevention of deaths.
“These results provide the tranquility we need for people who received Coronavac, showing that this is a vaccine that has a performance very similar to the others we have available”, says Juarez Cunha.
For the president of the SBIm, the study also reinforces the importance of getting vaccinated when an immunizing agent is available, and not waiting for a preferred brand to arrive, since vaccines used in Brazil have shown to have “great protection, especially for the moderate and severe forms of the disease”.
“The best vaccine is the one being applied to your arm at that moment,” says Cunha. “The choice of vaccine can make it take much longer for you to be vaccinated. The person will be wasting time to be protected from a disease that continues to happen in a very important way in our country”, explains the doctor.
The Chile study documented 218,784 Covid-19 cases, 22,866 hospitalizations, 7,873 ICU admissions, and 4,042 deaths among people from all groups (unvaccinated, partially, and fully vaccinated) in the period of analysis. Among the registered deaths, 3,633 occurred among the unvaccinated (2,786) and partially vaccinated (847).
Phase 3 of Coronavac in Turkey
Another study on Coronavac showed that the immunizing agent is safe and provides 83.5% protection against symptomatic Covid-19 and up to 100% in preventing hospitalization. Data are from Phase 3 of the Coronavac clinical trial in Turkey, which was published in the scientific journal The Lancet and presented at the European Congress of Microbiology.
The double-blind randomized clinical trial involved 10,029 adults aged 18 to 59 years (6,559 in the vaccine group and 3,470 in the placebo group) between September 2020 and January this year. There were 41 cases of symptomatic Covid-19; nine were in the vaccine group and 32 in the placebo group, which resulted in an 83.5% efficacy rate. There were no deaths. Six people who received a placebo were hospitalized and none of those vaccinated needed to be hospitalized.
According to the research authors, adverse effects of the vaccine were mostly mild and resolved within a day.
The analysis included a very young, healthy population and a very low follow-up period and was done before the emergence of worrying coronavirus variants, so the authors say the data is preliminary.
The average follow-up time was 43 days, shorter than anticipated because, while the study was ongoing, Coronavac was approved for emergency use in Turkey’s national vaccination campaign. Therefore, the research ethics committee decided that it would be unethical to continue giving placebos to volunteers, who ended up receiving the vaccine.