Immunogenicity of BNT162b2 COVID-19 vaccine in New Zealand adults

Abstract

BackgroundThere is very little known about SARS-CoV-2 vaccine immune responses in New Zealand populations at greatest risk for serious COVID-19 disease.MethodsThis prospective cohort study assessed immunogenicity in BNT162b2 mRNA vaccine recipients in New Zealand without previous COVID-19, with enrichment for Māori, Pacific peoples, older adults ≥ 65 years of age, and those with co-morbidities. Serum samples were analysed at baseline and 28 days after second dose for presence of quantitative anti-S IgG by chemiluminescent microparticle immunoassay and for neutralizing capacity against Wuhan, Beta, Delta, and Omicron BA.1 strains using a surrogate viral neutralisation assay.Results285 adults with median age of 52 years were included. 55% were female, 30% were Māori, 28% were Pacific peoples, and 26% were ≥65 years of age. Obesity, cardiac and pulmonary disease and diabetes were more common than in the general population. All participants received 2 doses of BNT162b2 vaccine. At 28 days after second vaccination, 99.6% seroconverted to the vaccine, and anti-S IgG and neutralising antibody levels were high across gender and ethnic groups. IgG and neutralising responses declined with age. Lower responses were associated with age ≥75 and diabetes, but not BMI. The ability to neutralise the Omicron BA.1 variant in vitro was severely diminished but maintained against other variants of concern.ConclusionsVaccine antibody responses to BNT162b2 were generally robust and consistent with international data in this COVID-19 naïve cohort with representation of key populations at risk for COVID-19 morbidity. Subsequent data on response to boosters, durability of responses and cellular immune responses should be assessed with attention to elderly adults and diabetics.

Robust immunogenicity of a third BNT162b2 vaccination against SARS-CoV-2 Omicron variant in a naïve New Zealand cohort

“…Nucleocapsid seroprevalence was used as a surrogate marker of previous SARS-CoV-2 infection. There are limitations in relying upon this marker as some individuals may not mount a nucleocapsid antibody response following SARS-CoV-2 infection, particularly if previously vaccinated, and these antibodies have been observed to wane over time [13,[20][21][22]. However, waning of anti-nucleocapsid antibodies is assay dependent, with the Roche total anti-nucleocapsid antibody assay, used in this study, reported to show high sensitivity out to at least 11.5 months post infection [23].…”

“…Anti-SARS-CoV-2-nucleocapsid specific antibodies (including IgG) Serum samples were analysed at Southern Community Laboratories in Dunedin (New Zealand). The electrochemiluminescence Elecsys® Anti-SARS-CoV-2 immunoassay (Roche Ltd) was used, in accordance with manufacturer instructions, to detect antibodies that recognise SARS-CoV-2 nucleocapsid protein in serum, which indicates prior infection [13]. Participants were tested at baseline (pre vaccination), prior to third dose and 28 days post third vaccine dose.…”

“…Binding antibodies specific to the Ancestral SARS-CoV-2 spike protein were quantified using the Abbott SARS-CoV-2 IgG II Quant immunoassay (Abbott Laboratories, Abbott Park, USA). This was conducted at Southern Community Laboratories, according to manufacturer's instructions as previously described [13].…”

“…Neutralising antibodies against Ancestral, Beta, Delta, and Omicron BA.1 variants of SARS-CoV-2 were quantified using the cPass SARS-CoV-2 Surrogate Virus Neutralisation Test (sVNT) (Genscript, Singapore), in accordance with the manufacturer's guidelines at the University of Auckland (New Zealand). This assay is validated against live viral neutralisation assays, and measures reduction in binding of recombinant spike and ACE2 proteins as a surrogate for neutralisation of viral infection [13,14]. Results were reported as percent (%) inhibition for all VoC.…”

“…A small number of participants were excluded after enrollment (n = 2) or lost to follow up (n = 8) at different timepoints (Figure 1). Twenty-eight days after second vaccination, 288 participants remained enrolled with 287 samples analysed [13]. At 6 months post second dose (prior to third dose), 273 participants remained in the study with immunogenicity analysis performed on 239 (anti-S IgG analysis and anti-nucleocapsid testing) and 236 (surrogate viral neutralisation testing) participants, respectively.…”