The Impact of Pneumococcal Vaccination on SARS-CoV-2 Infection in Health Care Workers Vaccinated Against Influenza in the 2021- 2022 Vaccination Campaign

Abstract

Introduction: Widespread administration of vaccines should be considered the best preventive strategy in Public Health. Influenza, pneumococcal disease, and Sars-CoV-2 are major public health problems. The last influenza vaccine season, as well as the previous one, took place in the midst of a pandemic. This led to the need to evaluate the possible relationship between influenza and pneumococcal vaccines in the susceptibility and severity of COVID-19 disease. Secondary bacterial infections (SBI) contribute to a significant proportion of influenza-related mortality, with Streptococcus pneumoniae as the main co-infecting pathogen. Vaccines against bacterial pathogens can reduce the incidence and severity of co-infections. The Influenza Vaccination Campaign runs annually for four months, from October 1 to January 31 of the following year; for the Pneumococcal Program, it is recommended to use the influenza vaccination campaign as an opportunity to immunize against pneumococcus as well. Aim of the study: The study aims to compare the trend of COVID infections - during the period from November 1, 2021 to May 31, 2022 - among health care workers who received regular flu vaccination, and to assess, whether among those who also received pneumococcal vaccination during their lifetime, they were better protected against SARS-CoV-2. Materials and Methods: The scenario was defined through extrapolation of data recorded in the Lazio Region's Regional Vaccine Registry (AVR). The sample of 964 individuals consisted of healthcare workers who underwent influenza vaccination during the last Vaccine Campaign (October 2021-January 2022 period) in the ASL of Viterbo. We explored the relationship between pneumococcal vaccination and COVID-19 test positivity. Within the identified cohort, the number of pneumococcal vaccinations administered over a lifetime and the swab positivity for Sars-CoV-2 was noted. The following data were considered: • Number of HCP who underwent influenza vaccination during the last vaccination campaign; • Number of HCP who underwent influenza vaccination who also received pneumococcal vaccination during their lifetime; • Number of HCP who underwent influenza vaccination and contracted SARS-CoV-2 during the period from November 1, 2021 to May 31, 2022; • Number of HCP who received influenza vaccination and also received pneumococcal vaccination during their lifetime and were infected with SARS-CoV-2 during the period from November 1, 2021 to May 31, 2022. Results: Analysis of the data collected shows that 65.5% of the healthcare workers in our sample, all of whom were vaccinated against influenza during the last Vaccination Campaign, did not contract Sars-CoV-2 infection during the observation period (November 1, 2021-May 31, 2022).