A Chilean study found that the first dose of vaccine alone does not protect against coronavirus disease 2019 (COVID-19). Chile is ahead of many South American countries in its vaccination program, anchored by the Chinese vaccine Coronavac.
This study by the University of Chile found that protection was only 27.7% two weeks after the second dose of the vaccine, and increased to 56.5% two weeks later.
However, for a single dose of vaccine, the 28-day protection between dose 1 and dose 2 was only 3 percent, consistent with the margin of error in such studies, the study noted.
After examining the effectiveness of the Chinese Coronavac vaccine versus the U.S. Pfizer vaccine, researchers estimated that Coronavac’s effectiveness was 54% in real life, consistent with the results of clinical trials in Brazil. Up to 93% of the vaccines administered in Chile were Coronavac.
In an Israeli study, the effect of the Pfizer vaccine was estimated to be about 94%.
Chile has a vaccinated population of about 15.2 million people, with 7.07 million people having received at least one dose of the vaccine and 4.04 million having received two doses to date.
Ennio Vivaldi, president of the University of Chile, said at a web conference, “Vaccination can very significantly reduce the likelihood of infection. Vaccines cannot eradicate an outbreak, but they can significantly reduce transmission, so you should get vaccinated anyway.”
But what the study also clearly shows is that the first dose of vaccine alone had no relevant effect after 4 weeks, meaning that those who were given the vaccine were actually as vulnerable as those who were not vaccinated at all.
The study also estimated that the number of cases of novel coronavirus infection in the 75- to 79-year-old group targeted at the beginning of the vaccine program would increase by more than 80 percent if the vaccine was not administered, and by 60 percent in the 70- to 74-year-old group.
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