Developing new COVID-19 vaccine against the variants is urgently needed rather than boosters: A longitudinal cohort study

Response and duration of serum anti‐SARS‐CoV‐2 antibodies induced by the third dose of an inactivated vaccine: A prospective longitudinal cohort study at 21 serial time points over 641 days

“…The fitting results of the power-law model in this study showed that the half-lives of neutralizing antibody, total antibody, and IgG antibody were 186.89, 363.04, and 417.5 days, respectively. Compared with a predicted half-life of 276 days after the third dose (Day 552), which was 191.57 days for neutralizing antibody, 410.37 days for total antibody, and 449.28 days for IgG antibody in our previous study, 7 the latest predicted half-life was slightly reduced, but it can still be considered there was a slow decay of antibody levels that came close to a plateau. Collectively, the decrease in vaccine-induced antibody titers over time was consistent with previous studies, but our latest data revealed that neutralizing antibodies decayed at a slow rate, while total antibody and IgG antibody remained at a high positive rate with a relatively longer half-life, suggesting that vaccine-induced overall antibody levels may remain protective 1 year after the third dose.…”

“…Based on the results of this cohort study over 641 days, a relatively higher level of antibodies was present 1 year after three doses of the vaccine. However, it is worth noting that vaccine‐induced anti‐SARS‐CoV‐2 antibodies have a lower neutralization capacity against Omicron variants, 19 which was the focus of our previous studies 7 . However, it was also reported that a booster dose restored the neutralizing efficacy of the vaccine during the Omicron variant epidemic, which was possibly due to the increasing breadth of humoral immunity and cross‐reactivity of the variant 19,20 …”

“…Our results addressed concerns about antibody attenuation and reconfirm the correctness and effectiveness of the booster dose strategy. Developing new COVID‐19 vaccines against the variants is more urgently needed than a booster dose (the fourth dose) at present, 7 but the booster is recommended because it may further increase anti‐SARS‐CoV‐2 antibody titers to counter the decreased neutralizing efficacy of antibodies during the epidemic of Omicron variants 21 . In addition, the age‐specific vaccination rate and the protective effect of the vaccine in vulnerable groups require attention, and the high‐risk groups, the elderly, and those with underlying medical conditions are strongly encouraged to receive a second booster dose as recommended in the current vaccination strategy.…”

“…Three subsets of anti-SARS-CoV-2 antibodies were detected in serum samples at 21 serial time points, and the distribution of antibody titers over time, which was defined as antibody kinetics, is presented as boxplots in Figure 2. The kinetics of three subsets of anti-SARS-CoV-2 antibodies within 552 days were detailed in our previous study, 7,8 in which the antibody titer rapidly increased to a peak level after the third dose, which was significantly higher than the peak antibody titer after the second dose and was followed by a slow decline. The antibody titer results on Day 641, 1 year after the third dose, showed that the titer levels of neutralizing antibody, total antibody, and IgG antibody dropped to about 10.78% (98.05 ± 109.66 IU/mL), 26.14% (152.8 ± 121.11 AU/mL), and 22.36% (7.68 ± 6.38 S/CO) of the peak value of the third dose, respectively.…”

“…Attenuation of anti-SARS-CoV-2 antibody levels after the first and second vaccine dose was confirmed in our previous studies, 6 and subsequent results showed that the antibody immune response was greatly enhanced after a third dose, but the antibody level slowly declined after reaching the peak level. 7 Therefore, the response and duration of serum anti-SARS-CoV-2 antibodies 1 year after the completion of a third dose of a novel coronavirus-inactivated vaccine are the aim of this study.…”