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\begin{document}

\title{Safety of Pfizer-BioNTech vaccine in a cohort of healthcare providers:
differences between na\selectlanguage{ngerman}ïve and previously infected.\selectlanguage{english}}



\author[1]{ANDREA CHONG VALBUENA}%
\author[1]{Isabel De-Jesus-Maria}%
\author[1]{Adriana Agurto-Ramírez}%
\author[1]{Francesc  Puchades Gimeno}%
\author[1]{Mercedes Melero-García}%
\affil[1]{General University Hospital Consortium of Valencia}%


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  \date{May 15, 2024}


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\begin{abstract}
Introduction: The Spanish Society of Immunology recently warned that a
history of past COVID-19 could result in a higher incidence of adverse
events (AEs) related to vaccination. We set out to analyze whether there
were any differences in AEs between healthcare workers vaccinated for
COVID-19 (either after the first or second dose) who had had a prior
diagnosis SARS-CoV-2 infection compared to those who had not had
COVID-19 before vaccination. Methods: This was a retrospective cohort
study in a population of healthcare workers. AEs related to the first
and second doses of the Pfizer vaccine were recorded. We compared the
incidence of AEs and compared individuals with 0--3 different AEs to
those with 4 or more AEs. The relative risks (RR) and their 95\%
confidence intervals were calculated. Results: Past infection was
associated with having more AEs after the first dose (p \textless{}
0.001), but not the second one (p = 0.476), as well as a higher
incidence of AEs (p \textless{} 0.001). Common AEs that were
statistically associated with past COVID infection included arthralgia,
asthenia, fever, chills, headache, and myalgia (p [?] 0.001). The RR for
having an increased absolute number of different AEs was 1.18 (95\%CI
{[}1.05, 1.33{]}) after the first dose and 1.05 (95\%CI {[}0.96,
1.14{]}) after the second dose. Conclusions: Our results showed that the
incidence of AEs was higher in individuals with a history of prior
COVID-19 infection.%
\end{abstract}%



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