Impact of Prior Influenza and Pneumoccocal Vaccines on Humoral and Cellular Response to SARS-CoV-2 BNT162b2 Vaccination

Vaccination against SARS-CoV-2 is considered the most effective method of prevention to contain the pandemic. While highly effective SARS-CoV-2 vaccines are being applied on a large-scale, whether and to what extent the strength of the vaccine-induced immune response could be further potentiated is still an object of debate. Several reports studied the effect of different vaccines on the susceptibility and mortality of COVID-19, with conflicting results. We aimed to evaluate whether previous influenza and/or pneumococcal vaccination had an impact on the specific immune response to the SARS-CoV-2 BNT162b2 mRNA vaccine. The study population consists of 710 workers from our Institute who completed the BNT162b2 schedule and have been tested at least once after the second dose, from 27 December 2020 up to 15 April 2021. Of these, 152 (21.4%) had received an influenza and 215 (30.3%) a concomitant influenza and pneumococcal vaccination, a median of 102 days before the second dose of BNT162b2. Overall, 100% of workers were tested for anti-Spike receptor-binding domain (anti-S/RBD) antibodies, 224 workers for neutralization titer (Micro-neutralization assay, MNA), and 155 workers for a spike-specific T cell interferon-γ response (IFN-γ). The levels of anti-S/RBD, MNA and IFN-γ were evaluated and compared according to sex, age, involvement in direct care of COVID-19 patients, and previous influenza/pneumococcal vaccination. At the univariate analysis, no statistically significant association was observed with regard to a previous influenza and pneumococcal vaccination. A significant lower anti-S/RBD response was observed according to an older age and male sex, while MNA titers were significantly associated to sex but not to age. At the multivariable analysis, workers receiving a concomitant influenza and pneumococcal vaccination or only influenza showed a 58% (p 0.01) and 42% (p 0.07) increase in MNA titers, respectively, compared to those who did not receive an influenza/pneumococcal vaccination. Female workers showed an 81% MNA and a 44% anti-S/RBD increase compared to male workers (p < 0.001). Compared to workers aged 21 to 49 years, those aged 50 or older were associated with a reduction in the anti-S/RBD (16%; p 0.005), MNA (31%; p 0.019), and IFN.g (32%) immune response. Maintaining the influenza and pneumococcal immunization program for the coming season, in which COVID-19 could still be spreading, remains strongly recommended to protect those who are more vulnerable and to limit the potential burden of these infections on the healthcare system.