Antibody-Mediated Immunogenicity Against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Following Priming, Boosting, and Hybrid Immunity: Insights From 11 Months of Follow-up of a Healthcare Worker Cohort in Israel, December 2020–October 2021

Abstract

Background We determined circulating anti-S SARS-CoV-2 IgG antibody titres in a vaccinated healthcare workers (HCWs) cohort from Northern Israel in the 11 months following primary vaccination according to age, ethnicity and previous infection status. Methods All consenting HCWs were invited to have their IgG levels measured before vaccination and at 6 subsequent timepoints using a quantitative S1/S2 IgG assay. All HCWs with suspected COVID-19 were PCR tested. We described trends in circulating IgG geometric mean concentration (GMC) by age, ethnicity, timing of boosting and previous infection status and compared strata using Kruskall-Wallis tests. Results Among 985 vaccinated HCWs, IgG titres between 1 month post 2 nd dose to pre-boosting gradually decreased in all age groups. Younger or previously infected individuals had higher initial post-vaccination IgG levels (p<0.001 in both cases); differences substantially decreased or disappeared at 7-9 months, before boosting. The proportion of individuals infected prior to initiating vaccination and re-infected after dose 1 was comparable to the proportion of breakthrough infection post-dose 2 in those not previously infected (4.2 vs 4.7%). Pre-infection IgG levels in the 40 participants with breakthrough infection after dose 2 were similar to levels measured at the same timepoint in vaccinated HCWs who remained uninfected (p>0.3). Post-dose3 IgG levels were more than 10-fold those 1month post-dose 2. Conclusions Immunity waned in all age groups and previously infected individuals, reversed by boosting. IgG titres decrease and reinfections in individuals with hybrid immunity (infection+vaccination) suggests they may also require further doses. Our study also highlights the difficulty in determining protective IgG levels.

Evaluation of S1RBD-Specific IgG Antibody Responses following COVID-19 Vaccination in Healthcare Professionals in Cyprus: A Comparative Look between the Vaccines of Pfizer-BioNTech and AstraZeneca

“…Regardless of vaccine type, all participants presented with positive levels of antibodies 3 weeks after the second vaccination dose, which remained positive 3 months after the second vaccine. These results agree with other studies showing that antibody levels can indeed last for months following vaccination [ 10 , 11 , 12 , 13 , 14 ]. Additionally, our findings are in line with other similar international studies, highlighting the decline of S1RBD-specific antibodies over time [ 10 , 11 , 12 , 13 , 14 , 15 ].…”

“…These results agree with other studies showing that antibody levels can indeed last for months following vaccination [ 10 , 11 , 12 , 13 , 14 ]. Additionally, our findings are in line with other similar international studies, highlighting the decline of S1RBD-specific antibodies over time [ 10 , 11 , 12 , 13 , 14 , 15 ]. Nevertheless, the immunogenic capacity of the antibodies present needs to be investigated further in order to determine their effectiveness in case of an infection with any of the emerging SARS-CoV-2 variants of concern.…”

“…Consequently, participants were asked to provide one further sample 3 months after the booster dose. Our results show a marked increase in antibody levels regardless of the booster type administered, as similarly observed in other studies [ 12 , 22 , 23 ]. Several studies have shown that the relative effectiveness of having a booster dose regardless of the primary vaccination regimen continues to outweigh the risks of having severe symptoms upon infection [ 21 , 22 , 24 ].…”

Seroprevalence and durability of antibody responses to AstraZeneca vaccination in Ugandans with prior mild or asymptomatic COVID-19: implications for vaccine policy

“…These data agree with the more extended durability of IgG and IgA relative to IgM antibodies ( 4 ), and the vaccine-induced expansion of S-IgG and IgA levels ( 5 , 30 ) demonstrated by other vaccines. In contrast, the Oxford-AstraZeneca vaccine elicited a more rapid immune response in this cohort than in two African studies ( 29 , 31 ), but agreed with an Israeli study where the peak occurred before three weeks ( 32 ).…”

SARS-CoV-2 Breakthrough Infections: Incidence and Risk Factors in a Large European Multicentric Cohort of Health Workers

“…A study involving all fully vaccinated Israeli adult population documented an increased infection rate with increasing time since vaccination, with a 1.6-to-2.1-fold higher rate of infection associated with a two-month increase in the time difference [20]. The growing evidence of the waning of vaccine-induced protection and natural immunity after 3-6 months has reinforced the need for a third dose, which has been shown to restore levels of neutralizing antibodies [21]. An observational study compared health workers (HWs) who received the two-dose regimen at least six months earlier with HWs who received a booster dose.…”