What happens to the Sinovac and Pfizer antibodies over time?

A new study that shows the national reality of the vaccination campaign against covid-19 found out what happens to antibodies as time passes. The conclusions: The positivity of IgG antibodies is maintained above 90% with Pfizer -after 20 weeks after its application-, while for Sinovac a progressive decrease in time is seen, dropping from the initial 75% (two weeks after the second dose), to around 40%.

The study was carried out with a representative sample of the entire country, which had the participation of more than 60 thousand people from 37 cities in the country -28 of the 29 local Health Services-.

It was prepared by researchers from the Complex Systems Engineering Institute (ISCI) and academics from the Faculties of Physical Sciences and Mathematics and Medicine of the University of Chile, together with the Undersecretary of Healthcare Networks.

How was it made?

The samples were taken at stations located at strategic points based on the mobility information of the large Chilean cities that ISCI in conjunction with ENTEL Ocean has been processing for more than a year. With fully aggregated and anonymized information, it was possible to select sites with a high volume of traffic that would allow a highly representative sample of each territory to be obtained.

In April 2020, the ISCI signed an alliance with the telephone company Entel to, together, work with mobility data and understand how people were behaving in the face of quarantines.

With close to 4 million data daily, the researchers were able -together with developing periodic reports regarding the real impact of quarantines in reducing displacement- define where to install the sampling stations, which served – after joint work with the Undersecretary of Healthcare Networks – as a base for the current study.

Unlike what happens with investigations that analyze the effectiveness of inoculations, that is, the performance of the vaccine in real conditions in the population in terms of cases and their severity, comparing vaccinated and unvaccinated cohorts, the study “Dynamic Seropositivity of IgG in Chile after the deployment of an inactivated virus vaccine (CoronaVac) and an mRNA vaccine (BTN162b2): a sentinel surveillance study”, analyzes the evolution over time of antibodies at the population level.

Indeed, by applying rapid tests for the detection of IgG antibodies against SARS-CoV-2, the study identifies the dynamics of these as time elapses since the inoculation of the first and second doses, in both types of vaccines . In addition, the study allows us to analyze whether positivity is affected by age, gender or comorbidities.

The detail of results

The report included the data of 64,813 people evaluated, until July 2, 2021, and within the main results shows that the general IgG positivity for Sinovac recipients reached 77% after full vaccination with two doses, while that a single dose of said vaccine produced low levels of IgG positivity, with 28.1%. Meanwhile, seropositivity in recipients of the Pfizer-BioNTech vaccine exceeded 95% after two doses and 80% after one dose of the vaccine.

Along with this, by age group, significantly lower levels of positivity were observed for both vaccines among participants aged 60 years and over compared to those under 40 years of age and, for Sinovac, for men compared to women and for people with diabetes and chronic heart disease.

As highlighted by the academic from the Faculty of Medicine of the U. de Chile, Dr. Miguel O’Ryan, the results show that “both the people who received the Sinovac vaccines and those who received Pfizer had a very robust response to IgG measured by the finger test within two weeks of the second dose: 75% for Sinovac and above 90% for Pfizer, which is very good for the clinical phase trials of both vaccines done previously, but this is in real life ”.

With these data in view, he warns, “you have to be very careful with the interpretation because that does not mean that people who have received Sinovac over time are necessarily unprotected, because we are only measuring one element of the immune response against the virus and with a technique ”.

These data, O’Ryan says, “Provide more evidence to suggest that a vaccination booster, fundamentally in the case of Sinovac”. At the same time, it confers immunological evidence that vaccination with two doses of Pfizer maintains high levels of IgG antibodies even 20 weeks after the second dose.

“It is very important to have scientific information on the behavior of immunity in people inoculated with different types of vaccines in our country, since it provides us with very relevant inputs to make decisions with local relevance regarding the management of the pandemic,” he said. part the undersecretary Alberto Dougnac.

“For the Undersecretariat of Assistance Networks it was essential to have participated in this study, fostering the teams that developed the field work and who managed to collect the information required by the investigation in 37 cities throughout the country,” said the Undersecretary.

Meanwhile, the academic from the Faculty of Medicine of the U. de Chile, Juan Pablo Torres placeholder image, says that it is important “to have the data when considering the types of vaccine that can be used for these booster types: it is important to have and generate evidence regarding the safety and the type of immune response that exists against that third booster dose , both in the people who are candidates to receive it, and in those who receive it to see their behavior over time ”.

For his part, the academic U. de Chile and director of the Complex Engineering Systems Institute (ISCI), Leonardo Basso, states that the results of the study “clearly show that the two vaccines generate responses, and that is great news that is consistent with the fact that the vaccination process has managed to stop the number of infections in more complex circumstances of the pandemic, given the circulation of a more contagious variant and much less effective quarantines ”. Likewise, he points out that “the study shows the differences over time, that is, how the IgG changes with respect to when a person was vaccinated, and in what way it is different for each vaccine, for people with comorbidity, for people over 60 years of age, for therefore, it can indicate where to prioritize third doses ”.

And, add Denis Saure, academic U. de Chile of ISCI, that to the extent that it is possible to “establish some type of correlation, between protection against the virus and IgG positivity, dynamic, fast and scalable monitoring can be done and that is what we are doing with In this study, we are establishing that relationship, we are first raising the base, well if there really is information in this IgG positivity, how this positivity is evolving in the population ”.

First publication made in Chile in The Lancet ID

The study was accepted in the important scientific publication. For Leonardo Basso, the size of the sample and the robustness of the results allowed the document to be published. “This information is solid, it has the enormous value of having been collected in partnership between the academy and the State, and it is not only relevant for Chile, it is relevant for all countries that have based their vaccination strategy on Sinovac,” he said.

For his part, for the academic Miguel O’Ryan, the research has an impact beyond our country, since by “showing all the countries of the world that are using COVID vaccines, that we must be looking at the differential response in the time, to evaluate the different vaccines and eventually see if the complementary strategy has to be adapted to the only initial incorporation of the vaccination, which is the key ”. It is also key to sustain this immunological surveillance in the population, especially to evaluate the effect of the booster doses over time, and to begin the evaluation of pediatric populations in light of the eventual initiation of vaccination in this group.

The Minister of Science, Andrés Couve, pointed out that “what we present today must really be seen as an achievement of a long-term vision that is based on associative and multidisciplinary research (…) These are very interesting results regarding antibody levels, but I would like to highlight how this The seroprevalence study has an impact on public health and how these results have been a key input when making the decision to apply the third dose in our country. This is a sample of Chilean science with an impact on public policy but also that contributes to the world. It will generate a debate, an interest not only in the study of seroprevalence but also in how Chilean science is positioned globally ”.

The study is still under development, with new samples daily in the national territory.


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