Systemic and Mucosal Humoral Immune Response Induced by Three Doses of the BNT162b2 SARS-CoV-2 mRNA Vaccines

• Published in: Vaccines (Basel) Vol. 10; no. 10; p. 1649
• Main Authors: Mancuso, Roberta, Agostini, Simone, Citterio, Lorenzo Agostino, Chiarini, Debora, Santangelo, Maria Antonia, Clerici, Mario
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.10.2022; MDPI
• Subjects: Analysis; Antibodies; BNT162b/Pfizer/Comirnaty; Coronaviruses; COVID-19; COVID-19 vaccines; Genes; Health care; humoral response; Immune response; Immune response (humoral); Immune system; Immunoassay; Immunoglobulin A; Immunoglobulin G; Medical personnel; Medical research; mRNA; mRNA vaccines; Mucosal immunity; Pandemics; Proteins; rehabilitation; Saliva; SARS-CoV-2; Severe acute respiratory syndrome coronavirus 2; Vaccines; Italy; United States > US; Switzerland
• ISSN: 2076-393X; 2076-393X
• DOI: 10.3390/vaccines10101649

BNT162b2 (BioNTech/Pfizer) was the first SARS-CoV-2 mRNA vaccine approved by the European Medicines Agency. We monitored the long-term humoral responses of healthcare workers (HCWs) who received three vaccine doses. A total of 59 healthcare workers were studied: 47 were never SARS-CoV-2-infected (naïve-HCWs), and 12 (infected-HCWs) recovered from COVID-19 before the first vaccine. Serum and saliva were collected at baseline (before the first dose), just before the second dose, 1, 3, 6, and 9 months after the second dose, and 10 days after the third vaccine. SARS-CoV-2-specific IgG and IgA were evaluated in serum and saliva, respectively, and the presence of neutralizing antibodies (NAb) was analyzed in serum. SARS-CoV-2-specific IgG peaked one month after the second vaccine in naïve-HCWs but right before this timepoint in infected-HCWs. IgG titers significantly decreased during follow-up and at month 9 were still detectable in 50% of naïve-HCWs and 90% of infected-HCWs. NAb were significantly decreased 6 months after the second vaccine in naïve-HCWs and 9 months after this dose in infected-HCWs. Salivary SARS-CoV-2-specific IgA titers were significantly higher in infected-HCWs and were undetectable 9 months after the second vaccine in 43% of the naïve-HCWs alone. The third vaccine greatly increased humoral IgG and mucosal IgA in both groups. Two BNT162b2 doses induced strong systemic and humoral immune responses; to note, these responses weakened over time, although they are more prolonged in individuals who had recovered from COVID-19. The third vaccine dose quickly boosts systemic and mucosal humoral responses.