Antibody response after two doses of the SARS-CoV-2 Comirnaty vaccine in a Covid-19 positive and Covid-19 negative Italian healthcare workers cohort

Abstract

Background

Extensive vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is now universally regarded as one of the most effective strategies for counteracting the current pandemic. The durability of the immune response of available vaccines is not known, therefore the quantitative dynamics of serum anti-S antibodies after Comirnaty vaccine in health care workers (HCW) of Desio Hospital was conducted.

Methods

51 previously infected and 198 not infected HCW, from Desio, Italy were enrolled in the study. Comirnaty double dose schedule was completed by each subject. Specific anti-S antibodies against the SARS-CoV-2 S protein were measured by ECLIA in sequential blood samples.

Results

A significant difference was observed beginning at pre priming dose (T0) of the anti-S antibodies between the two subgroups which persisted throughout the study (4 months). A significant reduction occurred after 4 months post-priming dose (T3). Finally, a subgroup of low and late responders with an increasing trend was found.

Conclusions

Specific anti-S antibodies are significantly decreased 4 months post priming dose of Comirnaty vaccine although prior COVID-19 infection seems to escalate humoral response. Further evaluation concerning antibody persistence beyond this point, and the proportion of neutralizing antibodies with higher affinity towards SARS-CoV-2 is needed, especially in naїve and immunosuppressed subjects.

Keywords:

• Covid-19
• anti-SARS-CoV-2
• Comirnaty
• vaccines
• humoral response

Acknowledgements

The authors are grateful to Stefano Signorini, Antonio Milano and Elena Galimberti for their help in sample collection, and Greta Casati, Silvia Pozzi, and Ilaria Zaccaria for their technical help.

Reagents and consumables were supplied by Roche in the framework of the scientific study “ABCV-Brianza (Anti-Bodies-Covid-Vaccino-Brianza)”

Disclosure statement

No potential conflict of interest was reported by the author(s).