Results of IgG Seropositivity of the Pfizer and Coronavac Covid-19 Vaccines in Chile

Results of IgG Seropositivity of the Pfizer and Coronavac Covid-19 Vaccines in Chile

Since the pandemic’s beginning, Chile has been one of the South American countries with the fastest response to prevent outbreaks. 81.3% of eligible adults in Chile had already received the first dose of the available Covid-19 vaccines by July 14. 75.3% of the vaccinated population received the CoronaVac vaccine, and the other 20.9 received the mRNA Pfizer BioNTech vaccine. Another authorized Covi-19 vaccine in Chile is the Astra Zeneca one. 

Researchers have compared the IgG positivity between the CoronaVac and Pfizer BioNTech Covid-19 vaccines in the South American country. It is important to have as much data as possible regarding the effectiveness of the available vaccines. 

Methodology of the investigation

The authors of the study published yesterday used volunteers from 28 testing stations for SARS-CoV-2 IgG detection and analyzed several data such as their vaccination status, types of vaccine, age, comorbidities, and other sociodemographic characteristics. Then, the researchers compared how many people vaccinated with CoronaVac tested positive for anti-SARS-CoV-2 IgG to those who received the Pfizer Covid-19 vaccine and tested positive for anti-SARS-CoV-2 IgG. The unvaccinated population was used as the control group of the study

Results and conclusions

The study analyzed more than 56 261 volunteers, 33 533 of them had received the CoronaVac vaccines, and 8947 had received the BNT162b2 vaccine, and 13 781 of them were part of the control group. The analysis showed that Sars-CoV-2 IgG positivity during week four after the first dose of the CoronaVac vaccine was 28.1%, while the IgG positivity after the first dose of the Pzifer vaccine was 79.4%. Three weeks after the second dose of the CoronaVac Coid-19 vaccine, the Sars-CoV-2 IgG positivity was 77.4% and for Pfizer was 96.5%.

The findings suggest that IgG seropositivity was lower after the CoronaVac Covid-19 vaccine than after the Pfizer one.


Anna is an avid blogger with an educational background in medicine and mental health. She is a generalist with many other interests including nutrition, women's health, astronomy and photography. In her free time from work and writing, Anna enjoys nature walks, reading, and listening to jazz and classical music.

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