key: cord-0335634-c9fg1ni6
authors: Kertes, J.; Baruch Gez, S.; Saciuk, Y.; Supino-Rosin, L.; Shamir Stein, N.; Mizrahi-Reuveni, M.; Ekka Zohar, A.
title: Effectiveness of the mRNA BNT162b2 vaccine six months after vaccination: findings from a large Israeli HMO
date: 2021-09-07
journal: nan
DOI: 10.1101/2021.09.01.21262957
sha: fb1d0e65fa19a9f82703501051e237cb9cd80f43
doc_id: 335634
cord_uid: c9fg1ni6

Israel is currently experiencing a new wave of CoVid-19 infection, six months after implementing a national vaccination campaign. We carried out three discrete analyses using data from a large Israeli HMO to determine whether IgG levels of those fully vaccinated drop over time, the relationship between IgG titer and subsequent PCR-confirmed infection, and compare PCR-confirmed infection rates by period of vaccination. We found that mean IgG antibody levels steadily decreased over the six-month period in the total tested population, and in all age groups. An inverse relationship was found between IgG titer and subsequent CoVid-19 infection (PCR-positive). Those participants vaccinated in the first two months of the campaign were more likely to become infected than those subsequently vaccinated. The 60+ vaccinated had lower initial IgG levels, and were at greater risk of infection. The findings support the decision to add a booster vaccine for those aged 60 and over.

Reserved space. Do not place any text in this section. Include the mandatory author checklist or your manuscript will be returned. Use continuous line numbering in your manuscript. population was categorized by vaccination completion: Jan-Feb 2021 and Mar-May 2021. For both 100 groups, the proportion that were tested PCR-positive between 9.6.2021-18.7.2021 (yes/no) was 101 calculated.

Statistical Analyses: Mann Whitney and Kruskal Wallis tests were carried out to compare antibody 103 levels over time between different population groups. Linear regression was used to identify those factors 104 associated with serology level. Ln of serology levels evidenced a normal distribution and was selected as 105 the outcome variable. Other variables entered into a hierarchical model were a) days from vaccination, b) 106 age, gender and socio-economic status, and c) selected chronic illnesses.

Chi square analyses were used to test the association between serology levels (categorized) with PCR 108 outcome. Serology status was categorized into below or equal to 300 AU/ml, or above 300 AU/ml.

Kaplan-Meier survival curves were calculated to compare time from serologic test to positive PCR result 110 for the serology categories using log-rank tests. Event was defined as positive PCR result. Time to event 111 was the number of days from serology test to PCR test, with censoring for those that died or left the 112 HMO, or had a follow up of less than 120 days. Logistic regression analysis was used to compare PCR-113 positive outcome between vaccination periods, while controlling for age group, socio-economic status 114 and presence of chronic illness (heart disease, HTN, diabetes, CKD, and immunosuppressive disorder).

Statistical analyses were carried out using SPSS, version 25 (BMI©) and R (version 3.6.2)

117 IgG antibody levels of the vaccinated population over time (N=8,395): 118 The description of the study population is provided in Table 1 . Of all HMO members who received both 119 vaccine doses, those subsequently tested for IgG antibodies were more likely to be male, younger (in the 120 18-44 age group), in a higher socio-economic bracket and less likely to have a chronic illness than those 121 not IgG tested.

Serology levels in the study population were found to decrease over time from a mean of 14,008 for 123 those tested within a month of being vaccinated to a mean of 1,411 for those tested in the sixth month 124 after vaccination (Table 4) . A decrease over time was observed in all sub-population groups, when 125 All rights reserved. No reuse allowed without permission. perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 7, 2021. ; https://doi.org/10.1101/2021.09.01.21262957 doi: medRxiv preprint Reserved space. Do not place any text in this section. Include the mandatory author checklist or your manuscript will be returned. Use continuous line numbering in your manuscript. demographic and health variables. We also established a clear association between serology levels and 177 subsequent risk of infection, wherein participants with a serology level of 300 AU/ml or lower were more 178 likely to get infected with CoVid-19 than those with a serology level above 300 AU/ml. Finally, we 179 established that those vaccinated at the beginning of the national vaccination campaign were more likely perpetuity. preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted September 7, 2021. ; https://doi.org/10.1101/2021.09.01.21262957 doi: medRxiv preprint Reserved space. Do not place any text in this section. Include the mandatory author checklist or your manuscript will be returned. Use continuous line numbering in your manuscript. perpetuity.

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

The copyright holder for this this version posted September 7, 2021. ; https://doi.org/10.1101/2021.09.01.21262957 doi: medRxiv preprint

Category No. (%) Not Tested N=79

3) 3,013 (58.6) Age Group < 18

Reserved space. Do not place any text in this section. Include the mandatory author checklist or your manuscript will be returned. Use continuous line numbering in your manuscript. Reserved space. Do not place any text in this section. Include the mandatory author checklist or your manuscript will be returned. Use continuous line numbering in your manuscript. Reserved space. Do not place any text in this section. Include the mandatory author checklist or your manuscript will be returned. Use continuous line numbering in your manuscript.