April 21, 2021

The CoronaVac vaccine has proven to be 89% effective in preventing ICU hospital admissions

The CoronaVac vaccine has proven to be 89% effective in preventing ICU hospital admissions
The Health Ministry presented the results of the first study, “Effectiveness of the inactivated CoronaVac vaccine against SARS-CoV-2 in Chile”. The analysis covered 10.5 million people, of whom 4 million were inoculated with the vaccine produced by the Sinovac laboratory between February 2 and April 1, 2021.

Dr. Rafael Araos, Advisor to the Undersecretariat of Public Health, released the results of the study, Effectiveness of the inactivated CoronaVac vaccine against SARS-CoV-2 in Chile.”

Participating in the release of the study were Dr. Enrique Paris, Health Minister, Dr. Paula Daza, Public Health Undersecretary, Dr. Alberto Dougnac, Healthcare Networks Undersecretary, and Dr. Cecilia González, Head of the National Immunization Program in Chile.

The Health Minister, Dr. Enrique Paris, said, “to arrive at where we are today, the vaccination process undertaken by the government of President Sebastian Piñera began in May 2020. This led to the arrival of the first doses of the vaccine against Covid-19 last December, and the beginning of the mass inoculation process over 70 days ago. This brings us to the results we are sharing today in this unprecedented study, ‘Effectiveness of the inactivated CoronaVac vaccine against SARS-CoV-2 in Chile,’ carried out by the Health Ministry.”

The purpose of this study, which will be updated monthly, is to provide a preliminary estimate of the effectiveness of the CoronaVac vaccine two months after initiating its mass use in Chile. To achieve this, the study compared the outcomes observed in a group of vaccinated and unvaccinated people, adjusted for age, sex, region of residence, income level, underlying medical conditions and nationality.

Currently in Chile, 12,726,959 doses have been administered, of which 7,600,908 correspond to the first dose and 5,126,051 to the second. This means that, of the target population of 15,200,840 to be vaccinated, 33.7% of these have been fully vaccinated. Of those inoculated, 90.1% have been inoculated with CoronaVac and 9.9% with Pfizer-BioNTech.

Dr. Rafael Araos, one of the authors of the study, explained that “the most important idea was that we have been able to study the effect in a cohort. In other words, we followed a group of vaccinated and unvaccinated people over time. Relevant variables were adjusted and the occurrence of events was compared between the two groups.” He added that the analysis covered 10.5 million people, of which, 4 million were inoculated with the CoronaVac vaccine between February 2 and April 1, 2021.

Dr. Araos indicated that the following three elements were considered for the statistical method:

  1. The level of instantaneous risk (Hazard Risk, HR) for each group and outcome, using the Cox Proportional Hazards model:

-        The time-dependent predictor variable (considering vaccination as a predictor variable in the time for each experimental unit)

  1. Effectiveness: 100% x 1 - HR
  2. Adjusted effectiveness

-       Age, sex, region of residence, income bracket, underlying health risks and nationality

Dr. Araos mentioned three important strengths of the study:

  1. Data collection and analysis:

-       Fast, results made it possible to study short-term effectiveness in “real time”

  1. Robust database:

-       Identification and evaluation of the relevant clinical outcomes

-       Adjusted for covariables

  1. Sample size:

-       Representativeness

-       Estimate of effectiveness in individuals partially and fully vaccinated

Dr. Rafael Araos said that “the effectiveness of CoronaVac 14 days after the second dose was 67% in preventing symptomatic Covid-19; 85% in preventing hospital admission; 89% in preventing ICU admission and 80% in preventing death due to Covid-19.” He explained further that “in plain language, if we take the 67% effectiveness in preventing Covid-19, of 100 people who would have had Covid-19, there would only be 33 cases if we were all vaccinated. Whereas, the 80% effectiveness in preventing death due to Covid-19 means that of 100 people who would have died due to the illness, 20 would die if we were all vaccinated.”

He added that these estimates are conservative and consistent with the preliminary results of phase 3 clinical trials in Brazil and Turkey and estimates given by the Universidad de Chile.

Dr. Araos added that to see the most benefits from the vaccine, the greatest number of people possible should be immunized, so it is hoped that soon groups of people will be added who were not initially included in the phase 3 clinical trials.

Among the recommendations, the expert explained that it is necessary “to follow the complete vaccination calendar as scheduled, maintain personal safety and hygiene measures and respect the restrictions on movement indicated by the healthcare authority.”

Finally, Dr. Rafael Araos concluded that “in a scenario of high epidemic activity, the vaccine studied was effective in preventing the symptomatic infection of SARS-CoV-2 and the most serious forms of the illness. Likewise, the importance of continuing the vaccination process should be emphasized, and its success depends in large part on attaining the broadest coverage possible. Considering that none of the vaccines are 100% effective, it is fundamental that we are all vaccinated.”

The Public Health Undersecretary, Paula Daza, thanked Dr. Araos and his team for this study, which showed positive results from the vaccine. “This study was possible for several reasons. First, Chile has a unique identification system, which has made it possible to monitor all vaccinated people from the start of the vaccine process. It is a very important study because it includes the monitoring of millions of people, which has allowed us to release these results today. What I want to say is that this study is important for Chile, but also for the world and the scientific community as it shows us that this vaccine is safe and we should continue with the vaccination process.”

Finally, the Health Minister, Enrique Paris, thanked “the Health Ministry, the National Immunization Program (PNI), the Health Planning Department, the Epidemiology Department, the Health Information and Statistics Department, the National Health Service (FONASA), the Public Health Institute (ISP), the Primary Healthcare Department (DIVAP), among others.”