Single-dose BNT162b2 mRNA COVID-19 vaccine significantly boosts neutralizing antibody response in health care workers recovering from asymptomatic or mild natural SARS-CoV-2 infection

Ilaria Vicenti; Francesca Gatti; Renzo Scaggiante; Adele Boccuto; Daniela Zago; Monica Basso; Filippo Dragoni; Maurizio Zazzi; Saverio Giuseppe Parisi

doi:10.1016/j.ijid.2021.05.033

Single-dose BNT162b2 mRNA COVID-19 vaccine significantly boosts neutralizing antibody response in health care workers recovering from asymptomatic or mild natural SARS-CoV-2 infection

Int J Infect Dis. 2021 Jul:108:176-178. doi: 10.1016/j.ijid.2021.05.033. Epub 2021 May 19.

Authors

Ilaria Vicenti¹, Francesca Gatti², Renzo Scaggiante³, Adele Boccuto⁴, Daniela Zago⁵, Monica Basso⁶, Filippo Dragoni⁷, Maurizio Zazzi⁸, Saverio Giuseppe Parisi⁹

Affiliations

¹ Department of Medical Biotechnologies, University of Siena, Viale Bracci 16, 53100 Siena, Italy. Electronic address: vicenti@unisi.it.
² Department of Molecular Medicine, University of Padova, Via Gabelli 63, 35100 Padova, Italy. Electronic address: francesca.gatti@asst-garda.it.
³ Belluno Hospital, Viale Europa 22, 32100 Belluno, Italy. Electronic address: renzo.scaggiante@aulss2.veneto.it.
⁴ Department of Medical Biotechnologies, University of Siena, Viale Bracci 16, 53100 Siena, Italy. Electronic address: boccuto2@student.unisi.it.
⁵ Department of Molecular Medicine, University of Padova, Via Gabelli 63, 35100 Padova, Italy. Electronic address: daniela.zago.3@studenti.unipd.it.
⁶ Department of Molecular Medicine, University of Padova, Via Gabelli 63, 35100 Padova, Italy. Electronic address: monica.basso@unipd.it.
⁷ Department of Medical Biotechnologies, University of Siena, Viale Bracci 16, 53100 Siena, Italy. Electronic address: dragoni16@student.unisi.it.
⁸ Department of Medical Biotechnologies, University of Siena, Viale Bracci 16, 53100 Siena, Italy. Electronic address: maurizio.zazzi@unisi.it.
⁹ Department of Molecular Medicine, University of Padova, Via Gabelli 63, 35100 Padova, Italy. Electronic address: saverio.parisi@unipd.it.

Abstract

Objectives: To measure SARS-CoV-2 neutralizing antibody (NtAb) titres in previously infected or uninfected health care workers who received one or two doses of BNT162b2 mRNA COVID-19 vaccine.

Methods: NtAbs were titrated as dose-inhibiting 50% virus replication (ID₅₀) by live virus microneutralization. We evaluated 41 health care workers recovering from mild or asymptomatic infection at first vaccination dose (T1_inf) and 21 days later (T2_inf). Sixteen uninfected health care workers were evaluated 20 days after first dose (T2_uninf) and 20 days after second vaccine dose (T3_uninf).

Results: At T2_inf, but not at T1_inf, there was a significant correlation between days from diagnosis (median 313, interquartile range 285-322) and NtAb levels (P = 0.011). NtAb titres increased at T2_inf with respect to T1_inf (1544 (732-2232) vs 26 (10-88), P < 0.001). Similarly, there was a significant increase in NtAb titres at T3_uninf compared with T2_uninf (183 (111-301) vs 5 (5-15), P < 0001). However, NtAb levels at T2_inf were significantly higher than those at T2_uninf and T3_uninf (P < 0.0001 for both analyses).

Conclusions: A single vaccination in people with mild or asymptomatic previous infection further boosts SARS-CoV-2 humoral immunity to levels higher than those obtained by complete two-vaccination in uninfected subjects.

Keywords: BNT162b2 mRNA COVID-19 vaccine; Health care workers; Neutralizing antibody response.

MeSH terms

Antibodies, Neutralizing
BNT162 Vaccine
COVID-19 Vaccines
COVID-19*
Health Personnel
Humans
RNA, Messenger
SARS-CoV-2*

Substances

Antibodies, Neutralizing
COVID-19 Vaccines
RNA, Messenger
BNT162 Vaccine