Coronavirus: study on efficacy of Sinovac and Pfizer vaccines relieves Uruguay

MONTEVIDEO.- The General Directorate of Health of the Ministry of Public Health (MSP) has published the first results on the vaccine efficacy against Covid-19 in Uruguay. The data reveals how the virus behaved in the population who have already received the two doses of Sinovac or Pfizer and who have also spent the 14 days necessary to complete the vaccination.

According to immunologist Álvaro Díaz, the data that brings “great peace of mind” are as follows: Sinovac vaccine prevents 95% of intensive care unit (ICU) admissions and Pfizer does it 99% of cases. Díaz points out that “even in a context where the P.1 variant is the most dominant”, it is “important” to know that intensive care admissions will decrease as people are vaccinated.

In reference to ability to avoid disease, the MSP report says that the Chinese vaccine does this with an efficiency of 57%, while that of Pfizer has a capacity of 75%.

There are several points to consider when analyzing this data. The doctor in biochemistry and specialist in applied immunology, Lucía Vanrell, underlines that “it is not fair” to compare the population vaccinated with Sinovac with that inoculated with Pfizer. This, he explains, has to do with the fact that those who received Sinovac are younger and therefore have better immune systems. They are also not as exposed to the virus as healthcare workers received by Pfizer, according to the vaccination schedule in Uruguay.

In this sense, Díaz mentions that 75% prevention for Pfizer is “predictable” from the spread of variant P.1., practically responsible for 100% of the cases detected today in the country.

“The variants of the virus do not imply any modification of the effectiveness of the vaccines against severe infections”, because “there is more a role of the immune system, the effectiveness of which is not modified by the variants”, explains Díaz. . And he adds: “Although they involve changes in the prevention of general disease.”

In addition, Pfizer studies published for phase 3 that were 95% effective were conducted in healthy people without co-morbidities nor previous pathologies.

Coronavac’s 57% efficacy in disease prevention is perhaps the scientific community’s most anticipated outcome, because very heterogeneous studies have been carried out all over the world and have given varied results.

A study of the Chilean population 65% effective in preventing symptomatic disease has served as a benchmark so far for local epidemiologists. For Uruguay, this 57% is conditioned by two factors: the age of those who received it and P.1.

In Chile, the variant originating in Manaus is not the most dominant as in Uruguay, which, according to Díaz, may explain the different result. However, he adds that, given that Chile vaccinated the most vulnerable people with Coronavac and this tends to reduce the effectiveness, the data from Uruguay should be better.

In summary, Díaz warns that the data released Thursday “is extremely reasonable”, although he points out that the MSP “should communicate what the confidence intervals were to know the margins of error”, which does not appear in the report. report published yesterday. .

Another Coronavac study was carried out by the Butantan Institute in Brazil. They measured the effectiveness of the vaccine in symptomatically preventing disease in healthcare workers and the result was 50.4%, less than in Uruguay.

Until, the Uruguayan study is the first to include all the positives. In studies conducted in other countries, efficacy was only measured in symptomatic patients.

Vanrell specifies that “we really do not know if they are symptomatic or not (those which were counted in Uruguay), it is simply all the people who went to take samples (after vaccination) and tested positive”.

The inclusion of those without symptoms “makes the figure more valuable” than 65% in Chile, according to Díaz.

Mortality and urinary tract infection

By observing the Vaccination data with Pfizer there is a significant comparison: it is more effective in avoiding intensive care admissions than in reducing the number of patient deaths.

In the breakdown of percentages, the report mentions that of the total number of people vaccinated with this vaccine, there were 681 with a positive swab, eight of whom died, but only one was admitted to intensive care. In addition, the document specifies that the deceased belonged in its entirety “to the group of 80 years and over”.

Díaz explains that the difference in Pfizer’s effectiveness in reducing mortality and reducing ICS admissions occurs because this adult population “often doesn’t make it to intensive care.” This happens because “invasive processes are carried out there to prolong life; a very old population can no longer bear this and doctors are committed to preserving the quality of life in these cases ”. As a result, older people with COVID-19 who die often do not do so in intensive care.

Daily cases

The study was carried out with data collected until Monday, May 25. The vaccination campaign coincided with the months with the highest number of deaths and infections. Even the week before the study was closed, Uruguay recorded two days with more than 4,500 daily cases.

What role does viral circulation play in efficacy studies? According to the immunologists consulted, the efficacy should not be impaired by many new cases of Covid-19.

Díaz points out that “with more circulation, the two groups are infected”, both vaccinated and unvaccinated “and then what is done is to compare them”.

The Country / GDA

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