Health and Fitness

Study explores profiles of COVID-19 vaccines across different countries

A recent study posted to the medRxiv* preprint server analyzed the amplitude, time, and adverse events (AEs) associated with seven coronavirus disease 2019 (COVID-19) vaccines across different countries.

Study: Analysis of immunization time, amplitude, and adverse events of seven different vaccines against SARS-CoV-2 across four different countries. Image Credit: Tong_stocker/Shutterstock

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines have played an imperative role in controlling the COVID-19 pandemic globally. However, there have been several reports of AEs following immunization (AEFIs) with COVID-19 vaccines. Yet, there is very little information available regarding the association of seroconversion with AEFI manifestations.  

About the study

The present study assessed the extent of SARS-CoV-2 antibody response observed after vaccination with the first and the second dose of BNT162b2 messenger ribonucleic acid (mRNA), ChAdOx1-S, mRNA-1273, Ad26.COV2, Ad5-nCoV, Coronavac, and GamCOVID-Vac vaccines. The team evaluated the SARS-CoV-2 spike (S) 1 and 2 immunoglobulin G (IgG) antibodies with previous medical conditions and severe and systemic adverse events (AEs).

This multicentric observational study involved volunteers who were fully vaccinated with either of the seven COVID-19 vaccines at five hospital centers from four different countries namely Mexico, Italy, Brazil, and Argentina in 2021. Consenting participants of any gender and age were included in the study while individuals who were vaccinated before the study were excluded.

On the vaccination day, the team collected a baseline sample (T0) from the participants, and the first vaccine dose was administered. The second (T1) and third (T2) samples, respectively, were obtained 21 days after the first and the second dose were administered.

The participants answered a questionnaire at each visit. The basal questionnaire acquired the medical history and SARS-CoV-2 infection history of the patient. Questionnaires answered following the first and second dose vaccinations recognized any AEFIs and noted the occurrence of any SARS-CoV-2 infection after vaccination. New COVID-19 infections among the participants were also monitored using polymerase chain reaction (PCR) testing.

The primary outcome of the study was the association of magnitude of SARS-CoV-2 antibody response with vaccinations, considering previous conditions and AEFIs. A chemiluminescence immunoassay (CLIA) was used to evaluate the levels of anti-S1 and anti-S2 IgG antibodies produced against SARS-CoV-2 in the plasma samples. For this assay, the results were classified as negative for levels below 12.0 arbitrary units (AU)/ml, indeterminate for levels between 12.0 AU/ml and 15.0 AU/ml, and positive for levels over 15 AU/ml.


The study results showed that out of the 1,867 patients recruited, 1,352 were from Mexico, 260 from Brazil, 213 from Argentina, and 42 from Italy. The average age of the participants was 52 years and 52% were men, while 30% suffered from obesity, and 26.8% suffered from hypertension. Also, the ChAdOx1-S vaccine was received by 666 subjects, Coronavac by 582, BNT162b2 mRNA by 289, Gam-COVID-Vac by 213, mRNA-1273 by 65, Ad26.COV2 by 31, and Ad5-nCoV by 19 subjects.

Participants were deemed SARS-CoV-2 positive if they had a PCR-confirmed test or if levels of specific anti-S1 and anti-S2 IgG antibodies against SARS-CoV-2 in their samples were over 15 AU/ml at baseline. Also, 627 participants reported SARS-CoV-2 infection before the study, among which 24.8% were vaccinated with ChAdOx1-S, 42.2% with Coronavac, 37.1% with BNT162b2 mRNA, 25.8% with Gam-COVID-Vac, 47.6% with mRNA-1273, 58% with Ad26.COV2, and 26% with Ad5-nCoV.

The naïve patients showed the highest increase in antibody levels after the first dose of mRNA-1273 vaccination, followed by BNT162b mRNA and Ad5-nCoV and after the second dose of mRNA-1273, followed by BNT162b mRNA and Gam-COVID-Vac.

In subjects with a history of SARS-CoV-2 infection, the highest improvement in antibody levels was observed post-first dose vaccination with mRNA-1273, followed by BNT162b mRNA and ChAdOx1-S and after the second dose of mRNA-1273, followed by Gam-COVID-Vac and BNT162b mRNA. On comparing BNT162b mRNA and mRNA-1273, the latter induced a higher alteration in antibody levels while the rest of the vaccines showed lesser change.

The study noted a minimum of one AEFI in 71% of the participants post the administration of the first BNT162b2 mRNA dose, 93% post-mRNA-1273, 38% post-Gam-COVID-Vac, 42% post-Coronavac, 51% post-ChAdOx1-S, 74% post-Ad5-nCoV, and 81% post-Ad26.COV2. A total of 65%, 23%, 23%, 88%, and 33% of participants had a minimum of one AEFI after the second dose vaccination with BNT162b2 mRNA, Gam-COVID-Vac, ChAdOx1-S, mRNA-1273, and Coronavac, respectively.

After receiving the first dose of BNT162b2 mRNA, Gam-COVID-Vac, ChAdOx1-S, Ad26.COV2, mRNA-1273, Coronavac, and Ad5-nCoV, a total of 85%, 95%, 67%, 57%, 80%, 84%, and 93% of the patients reported “very mild” or “mild” symptoms, respectively. After the administration of the second dose of BNT162b2 mRNA, Gam-COVID-Vac, ChAdOx1-S, mRNA-1273, and Coronavac, almost 82%, 98%, 76%, 49%, and 89% of the patients had “very mild” or “mild” symptoms, respectively.


To summarize, the study findings showed that the magnitude of SARS-CoV-2 seroconversion was dependent on the age, type of vaccine, and history of SARS-CoV-2 infection. Also, the AEFIs were correlated with age, gender, and type of vaccine and positively associated with antibody responses.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

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