Breakthrough infections and waning immune responses with ChAdOx1 nCoV‐19 or mRNA vaccine in healthcare workers

Abstract

Dear Editor,Breakthrough infection of SARS-CoV-2 has been increased according to the emergence of the delta variant and vaccine-induced waning immunity. 1 In addition, epidemiologic studies have reported that people with previous SARS-CoV-2 infection show decreasing antibody levels against SARS-CoV-2 2 and can be reinfected with the virus later on. 3 Here, we assessed the waning vaccine effectiveness by comparing the breakthrough infection rate between healthcare workers (HCWs) vaccinated with two doses of ChAdOx1 nCoV-19 (ChAdOx1) or mRNA vaccine. We also compared immune responses against ancestral SARS-CoV-2 and the delta variant between individuals with natural infection and HCWs who received the ChAdOx1 or BNT162b2 vaccine.This study was performed at Asan Medical Center with 15,034 HCWs, Seoul, South Korea. First, we retrospectively compared the breakthrough infection rate in HCWs who were vaccinated with two doses of ChAdOx1 or mRNA vaccine. We evaluated the infection rates stratified by 30-or 60-day interval and by vaccine type in each period. Second, we conducted a 6-month longitudinal prospective study in HCWs who either received two doses of ChAdOx1 or BNT162b2 vaccines and individuals with previous SARS-CoV-2 infection. The detailed methods for enrolment, evaluation of breakthrough infection rates and measurement of immune responses are described in Supporting Information.As of December 15, there were 14,427 fully vaccinated HCWs (ChAdOx1, n = 9717; mRNA-1273, n = 1441; BNT162b2, n = 1297; other n = 1972). Most of the HCWs (82%, 7966/9717) vaccinated with the ChAdOx1 vaccine received their first dose in March, and most of the HCWs vaccinated with the mRNA vaccine received their first dose between June and September (84%, 2305/2738, Figure 1A). Of the 12,455 HCWs who were fully vaccinated withThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Preparedness for further boosting coronavirus disease 2019 vaccines

“…wileyonlinelibrary.com/journal/ctd2 1 of 2 https://doi.org/10.1002/ctd2.55 two-dose COVID-19 vaccination drive in the delta-variant dominant era. 6 Neutralizing antibody levels against the delta variant after two-dose COVID-19 vaccination declined more rapidly than those after natural SARS-CoV-2 infection. 6 Thus, the breadth and durability of neutralizing antibodies might be wider and longer, respectively, after natural SARS-CoV-2 infection than after COVID-19 vaccination.…”

“… 6 For these reasons, breakthrough infection rates sharply increased 6 months after the two‐dose COVID‐19 vaccination drive in the delta‐variant dominant era. 6 …”

“…Neutralizing antibody levels against the delta variant after two‐dose COVID‐19 vaccination declined more rapidly than those after natural SARS‐CoV‐2 infection. 6 Thus, the breadth and durability of neutralizing antibodies might be wider and longer, respectively, after natural SARS‐CoV‐2 infection than after COVID‐19 vaccination. However, the new, highly transmissible omicron variant can easily evade natural infection‐induced immunity.…”

“…So, the decrease in symptomatic COVID‐19 protection has been well linked to a waning antibody response following a two‐dose COVID‐19 vaccination regimen 5 . Further, the emergence of SARS‐CoV‐2 variants that can evade vaccine‐induced immunity facilitated the breakthrough infection, since circulating neutralizing antibody levels against these immune‐evasive variants were lower 6 . For these reasons, breakthrough infection rates sharply increased 6 months after the two‐dose COVID‐19 vaccination drive in the delta‐variant dominant era 6 …”

“…Further, the emergence of SARS‐CoV‐2 variants that can evade vaccine‐induced immunity facilitated the breakthrough infection, since circulating neutralizing antibody levels against these immune‐evasive variants were lower 6 . For these reasons, breakthrough infection rates sharply increased 6 months after the two‐dose COVID‐19 vaccination drive in the delta‐variant dominant era 6 …”