key: cord-0292929-xre1l41y
authors: Kato, H.; Miyakawa, K.; Ohtake, N.; Yamaoka, Y.; Yajima, S.; Yamazaki, E.; Shimada, T.; Goto, A.; Nakajima, H.; Ryo, A.
title: Vaccine-induced humoral and cellular immunity against SARS-CoV-2 at 6 months post BNT162b2 vaccination
date: 2021-10-30
journal: nan
DOI: 10.1101/2021.10.30.21265693
sha: d98436d9ca95ce16ad5ec7be26d6be41158e8b86
doc_id: 292929
cord_uid: xre1l41y

To evaluate vaccine-induced humoral and cell-mediated immunity at 6 months post BNT162b2 vaccination, immunoglobulin G against SARS-CoV-2 spike protein (SP IgG), 50% neutralizing antibody (NT50), and spot-forming cell (SFC) counts were evaluated by interferon-{gamma} releasing ELISpot assay of 98 healthy subjects (median age, 43 years). The geometric mean titers of SP IgG and NT50 decreased from 95.2 (95% confidence interval (CI) 79.8-113.4) to 5.7 (95% CI 4.9-6.7) and from 680.4 (588.0-787.2) to 130.4 (95% CI 104.2-163.1), respectively, at 3 weeks and 6 months after the vaccination. SP IgG titer was negatively correlated with age and alcohol consumption. Spot-forming cell counts at 6 months did not correlate with age, gender, and other parameters of the patients. SP IgG, NT50, and SFC titers were elevated in the breakthrough infected subjects. Although the levels of vaccine-induced antibodies dramatically declined at 6 months after vaccination, a certain degree of cellular immunity was observed irrespective of the age.

Severe acute respiratory coronavirus-2 (SARS-CoV-2) vaccine is a powerful tool to control the coronavirus disease-2019 (COVID-19) pandemic and the mRNA vaccine BNT162b2 (Pfizer-BioNTech, USA) is reported to have an vaccine efficacy of 95% [1] .

However, the long-term decline in efficacy has been a major concern regarding the efficacies of most vaccines in preventing infection; reportedly, most vaccines exhibit declining efficacies after 6 months after the vaccination [2, 3] . However, the efficacy of a vaccine in preventing severe disease is reported to remain at a high level. The titer of immunoglobulins (IgG) against spike proteins (SPs) induced by the vaccine dropped to 7% in 6 months [4] . The decline in the efficacy for preventing the infection can be attributed to the decrease in antibody titer, although the prevention of severe disease cannot be explained by antibody titer alone and cellular immunity may be involved. mRNA vaccines induce not only humoral immunity but also cellular immunity [5] . We previously evaluated IgG against SARS-CoV-2 SP (SP IgG) by chemiluminescent enzyme immunoassay (CLEIA) before and up to 6 weeks after the first dosing with BNT162b2 vaccine [6] . In this study, we analyzed the SP IgG level against the original and Delta strains by CLEIA and 50% neutralizing titer (NT50) at 6 months after vaccination. In addition, SARS-CoV-2-specific T-cell response was evaluated by interferon γ (IFN-γ) releasing ELISpot assay to assess the status of cellular immunity at 6 months after vaccination. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The healthcare workers at the Yokohama City University Hospital who had completed two doses of the BNT162b2 vaccine (Comirnaty 30µg, Pfizer/BioNTech, USA) given intramuscularly on the deltoid muscle (lot number: EP9605 as a first dose and ER9480 as a second dose) from March to April 2021 at 3-week interval were recruited in this study.

For the 6-month post-vaccination evaluation, the blood samples were drawn at 180 ±15 days after the second dose of vaccination. The subjects' information, including the date of birth, sex, current drinker, current smoker, comorbidities, body height, and body weight at the time of first dose of vaccination were obtained. The participants' age and body mass index (BMI) at the time of first vaccination was then calculated.

Immunoglobulin G titer against SP and nucleocapsid (NP) IgG were determined using the commercial chemiluminescent enzyme immunoassay (AIA-CL SARS-CoV-2 SP IgG antibody detection reagent, Tosoh, Japan). Furthermore, the IgG index values between the original and Delta stain (D614G, T478K, P681R, and L452R) were measured and compared as previously described [6] . PBMCs.

Continuous data were presented either as means with 95% CI or medians with interquartile range (IQR). Categorical data were presented as numbers and percentages.

Continuous variables between the two groups were compared using the two-tailed Mann-Whitney U-test. Categorical data were compared using the Fisher's exact test. The correlation between two continuous numbers was calculated by Spearman's correlational analysis. A multivariable regression model was employed to investigate the association between the background variables and antibody titers. The SP IgG index values were logtransformed for analysis to remove positive skewness. Statistical analyses were . CC-BY 4.0 International license It is made available under a perpetuity.

is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted October 30, 2021. Table 1 ).

At 6 months of receiving the second dose of BNT162b2 vaccine, SP-specific IgG decreased markedly, with a mean GMT decreasing from 95.2 at 3 weeks after vaccination to 5.7 at 6 months. A previous report showed a peak at 1 week after 2 doses and a decrease to 7% at 6 months [4] . Our data using the CLEIA method demonstrated a surprising decrease to 1/15 after 3 weeks of vaccination, and the same trend was noted for NT50, which also depicted a marked decrease. However, the correlation between cellular immunity assessed by SP-specific T-cell response and the SP IgG index titer and NT50 was weak, suggesting that cellular immunity may have a different dynamic from antibody titer. In this study, the SP-specific T-cell response in this study was 84 SFC/10 6 PBMCs.

The previously reported SP-specific T-cell response immediately after vaccination was 184 SFC/10 6 PBMCs after two doses of BNT162b2 vaccine [7] . The ELISpot assay at 6 months in naturally infected individuals reported 97 (IQR 38-143) SFC/10 6 PBMCs, and the SP-specific T-cell response observed in the study participants at 6 months postvaccination was not significantly different from that observed in naturally infected individuals (P = 0.865, calculated using supplemental data from reference [8]). There seemed no difference between cellular immunity conferred by natural infection and the reduction in cellular immunity by vaccines. It has been previously reported that the antibody titer is negatively correlated with age up to 6 months after vaccination [9], but SP-specific T-cell response has not been related to age [10]. In our study, there was no correlation among age, gender, BMI, alcohol, or smoking. The decline in cellular immunity was slower than that of antibody titer, indicating it to be less negatively correlated with age, which possibly explains its long-term effect in protecting from developing the severe form of this disease.

In this study, four cases of breakthrough infection after the second vaccination were investigated. It is believed that a high antibody titer was induced in patients with breakthrough infection. Although the titer of antibodies against SP of the Delta strain was . CC-BY 4.0 International license It is made available under a perpetuity.

is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted October 30, 2021. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint

The copyright holder for this this version posted October 30, 2021. ; https://doi.org/10.1101/2021.10.30.21265693 doi: medRxiv preprint

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