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Archivos de Prevención de Riesgos Laborales

versión On-line ISSN 1578-2549

Arch Prev Riesgos Labor vol.26 no.3 Barcelona jul./sep. 2023  Epub 27-Nov-2023 

Letters to the Editor

Response to the letter to the editor "Commentary on the COVID-19 mRNA vaccine reactogenicity study"

Joan Inglés-Torruella1  , Rosa Gil-Soto1  , Esther Sabaté1  , Mercé Garcia-Grau1  , Nina Pons-Boronat2  , Adelaida Rubio-Civit2  , Miriam Bandera-Baez1  , Gustavo Moreno-Martín1 

1Salut Sant Joan Reus - Baix Camp. Hospital Universitari Sant Joan. Reus. Tarragona. España

2Facultad de Medicina. Universitat Rovira i Virgili. Reus. Tarragona. España.

Dear Editor,

Our study aims to compare the short-term adverse effects and their consequences between the RNAm vaccines Commirnaty® (Pfizer) and Spikevax® (Moderna), as well as these short-term adverse effects and their consequences between the first and second doses of these vaccines with each other. Possible long-term adverse effects were not the subject of our study1.

From the results obtained, it is clear that second doses of both types of mRNA vaccines generate a higher rate of adverse effects than first doses of the same vaccines. Specifically, second doses have an adverse effect for Commirnaty® in 75.64% (95%CI: 73.18-78.10) of those vaccinated and for Spikevax® in 87.85% (95%CI: 81.66-94.04), while first doses for Commirnaty® represented a rate of 67.83% (95%CI: 65.74-69.91) and for Spikevax® 76.10% (95%CI: 71.97-80.23) of those vaccinated.

On the other hand, if one vaccine is compared with the other, the rate of adverse effects of Spikevax® vaccine was higher than that observed for Comirnaty®, both for the first dose OR 1.51 (95%CI: 1.18-1.93) and for the second dose OR 2.32 (95%CI: 1.28-4.22).

The differences in the rate of adverse effects between the two vaccines could be explained by a larger volume of drug injected (0.5 versus 0.3 mL), a higher amount and concentration of mRNA contained in each vaccine (200 μgr/mL versus 100 μgr/mL) (1) or by the different concentration of adjuvants and excipients contained in each vaccine. However, in our study we did not consider the possibility of having had COVID-19 prior to vaccination, since we did not have serology or other laboratory parameters of vaccine recipents that would allow us to identify whether or not they had had COVID-19 prior to vaccination. Considering that having had COVID-19 prior to vaccination may induce greater reactogenicity against the vaccine2-6, not including this variable in the analysis could lead to biased results. However, the distribution of subjects to receive one or the other vaccine was random and close in time (from January to August 2021) and the overall rate of COVID-19 at the time of administering either vaccine was most probably similar. Therefore, it seems unlikely that the probability of being infected by the SARS-CoV-2 prior to receiving the vaccine was higher for the Spikevax® group compared to the Comirnaty® group, and that could explain the observed differences. Finally, other authors also found a higher reactogenicity after the Spikevax® than with the Comirnaty® vaccine(2, 7-9).


1. Inglés Torruella J, Gil Soto R, Sabaté E, Garcia Grau M, Pons Boronat N, Rubio Civit A, Bandera Baez M, Moreno Martín G. Estudio de reactogenicidad en las vacunas mRNA frente a la COVID-19. Arch Prev Riesgos Labor. 2023;26(2):106-126. [ Links ]

2. Parés-Badell O, Martínez-Gómez X, Pinós L, Borras-Bermejo B, Uriona S, Otero-Romero S, et al. Local and Systemic Adverse Reactions to mRNA COVID-19 Vaccines Comparing Two Vaccine Types and Occurrence of Previous COVID-19 Infection. Vaccines. 2021;9:1463. [ Links ]

3. Tré-Hardy M, Cupaiolo R, Papleux E, Wilmet A, Horeanga A, Antoine-Moussiaux T, et al. Reactogenicity, safety and antibody response, after one and two doses of mRNA-1273 in seronegative and seropositive healthcare workers. J Infect. 2021;83(2):237-279. [ Links ]

4. Krammer F, Srivastava K, Simon V. Robust spike antibody responses and increased reactogenicity in seropositive individuals after a 1 single dose of SARS-CoV-2 mRNA vaccine. MedRxiv. 2021. [ Links ]

5. Raw RK, Kelly CA, Rees J, Wroe C, Chadwick DR. Previous COVID-19 infection, but not Long-COVID, is associated with increased adverse events following BNT162b2/Pfizer vaccination. J Infect. 2021;83(3):381-412. [ Links ]

6. Mathioudakis AG, Ghrew M, Ustianowski A, Ahmad S, Borrow R, Papavasi-leiou LP, et al. Self-Reported Real-World Safety and Reactogenicity of COVID-19 Vaccines: A Vaccine Recipient Survey. Life (Basel). 2021;11(3):249. [ Links ]

7. Centro de Coordinación de Alertas y Emergencias Sanitarias. Actualización nº 630. Enfermedad por el coronavirus (COVID-19). 02.09.2022. [Cited September 02, 2022]. Available at: ]

8. Centers for Disease Control and Prevention. The Moderna COVID-19 Vaccine's Local Reactions, Systemic Reactions, Adverse Events, and Serious Adverse Events. [Cited October 07, 2022.] Available at: ]

9. Centers for Disease Control and Prevention. Pfizer-BioNTech COVID-19 Vaccine Reactions & Adverse Events. [Cited October 07, 2022.] Available at: ]

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