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. 2023 Mar 28;11(4):744.
doi: 10.3390/vaccines11040744.

Salivary Antibody Responses to Two COVID-19 Vaccines following Different Vaccination Regimens

Hassan Alkharaan  1 , Hatem Al-Qarni  2   3 , Muath A Aldosari  4   5 , Mohammed Alsaloum  2   3 , Ghada Aldakheel  2 , Mohammed W Alenazi  6 , Naif Khalaf Alharbi  6   7
Affiliations

Salivary Antibody Responses to Two COVID-19 Vaccines following Different Vaccination Regimens

Hassan Alkharaan et al. Vaccines (Basel). .

Abstract

Background: To date, little is known about the salivary mucosal immune response following different COVID-19 vaccine types or after a booster (3rd) dose of the BNT162b2 (BNT) vaccine. Methods: A total of 301 saliva samples were collected from vaccinated individuals and arranged into two cohorts: cohort 1 (n = 145), samples from individuals who had received two doses against SARS-CoV-2; cohort 2 (n = 156), samples from individuals who had received a booster of BNT vaccine. Cohorts 1 and 2 were sub-stratified into three groups based on the types of first and second doses (homologous BNT/BNT, homologous ChAdOx1/ChAdOx1, or heterologous BNT/ChAdOx1vaccinations). Salivary immunoglobulin G (IgG) response to SARS-CoV-2 spike glycoprotein was measured by ELISA, and clinical demographic data were collected from hospital records or questionnaires. Results: Salivary IgG antibody responses against different vaccines, whether homologous or heterogeneous vaccination regimens, showed similar levels in cohorts 1 and 2. Compiling all groups in cohort 1 and 2 showed significant, albeit weak, negative correlations between salivary IgG levels and time (r = -0.2, p = 0.03; r = -0.27, p = 0.003, respectively). In cohort 2, the durability of salivary IgG after a booster dose of BNT162b2 significantly dropped after 3 months compared to the <1 month and 1-3 months groups. Conclusions: Different COVID-19 vaccine types and regimens elicit similar salivary anti-SARS-CoV-2 IgG with modest waning over time. Boosting with BNT162b2 vaccine did not produce an evident increase in mucosal IgG response whereby COVID-19 recovered subjects show higher salivary IgG than naive, post-vaccination subjects. The ChAdOx1/ChAdOx1 regimen showed better correlation between salivary IgG levels and durability. These findings highlight the importance of developing oral or intra-nasal vaccines to induce stronger mucosal immunity.

Keywords: COVID-19; ELISA; IgG; SARS-CoV-2; antibody; immune responses; mucosal; saliva; vaccines.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Comparisons between a commercial and the in-house ELISA were performed using a panel of 21 saliva samples (A) to validate anti-SARS-CoV-2 spike protein IgG in-house assay performance in saliva. The vaccine-induced antibodies against SARS-CoV-2 Spike-protien between different vaccine types after 2nd dose (B) and 3rd dose (C) were evaluated in non-infected COVID-19 individuals. Salivary IgG levelsafter BNT booster (cohort 2) were grouped based on time since the 3rd dose into (1) less than 1 month, (2) 1–3 months, and (3) more than 3 months (D). The levels of salivary IgG before and after the BNT booster dose (E) and between previously COVID-19 infected individuals and non-infected individuals (F) were compared. A nonparametric Mann–Whitney U test for significance was performed. BNT, BNT162b2 vaccine. ChAdOx1, ChAdOx1 nCoV-19 vaccine.
Figure 2
Figure 2
Correlation between salivary IgG levels and time since the 2nd dose (A) and 3rd dose (B) following different vaccination regimens. Spearman correlation analysis was used to determine rho and p values.
See this image and copyright information in PMC

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