key: cord-0940928-cpqzsvxx
authors: Cao, Yunlong; Hao, Xiaohua; Wang, Xi; Wu, Qianhui; Song, Rui; Zhao, Dong; Song, Weiliang; Wang, Yao; Yisimayi, Ayijiang; Wang, Wei; Zhang, Wen; Du, Juan; Yu, Hongjie; Xie, Xiaoliang Sunney; Jin, Ronghua
title: Humoral immunogenicity and reactogenicity of CoronaVac or ZF2001 booster after two doses of inactivated vaccine
date: 2021-12-03
journal: Cell Res
DOI: 10.1038/s41422-021-00596-5
sha: 40d641b03d908d59391fdb95dd04dcc54dc5f460
doc_id: 940928
cord_uid: cpqzsvxx

nan

and physical examination.

3) Female subjects of childbearing age have no lactation or pregnancy (negative urine pregnancy test) at the time of enrollment or no plan for family within the first 3 months after enrollment, take effective contraceptive measures within 2 weeks before enrollment. 4) Participants must provide consent indicating that he or she understands the purpose, procedures and potential risks and benefits of the study, and is willing to participate in the study and adhere to the procedures specified in the protocol.

1) Positive results for RT-qPCR tests of SARS-CoV-2.

2) Participant has clinical symptoms including fever, hoose, fatigue, stuffy nose, runny nose, sore throat, myalgia, diarrhea, shortness of breath, dyspnea, etc.

3) temperature ≥37.0ºC prior to vaccination. 15) Participant received other study drugs within 3 months before enrollment; 16) Any condition or situation precluding or interfering the compliance with the protocol assessed by investigators.

Solicited local and systemic adverse reactions were collected by investigators on each visit. The severity of adverse reactions was graded according to Common Terminology Criteria for Adverse Events (version 5.0). The existence of causal associations between adverse events and vaccination was determined by the investigators.

The primary outcome was seroconversion rate on day 14 after the third dose of neutralizing antibodies to authentic SARS-CoV-2, which was defined as a change of titers from seronegative at baseline to seropositive, or a four-fold increase of titers for individuals whose titers were above seropositive cutoffs (1:8). Secondary immunological outcomes included geometric mean titers (GMTs) of neutralizing antibodies to infectious SARS-CoV-2 and pre-immunization (baseline) and on day 14 after third doses. Blood samples of participants in the control group were taken on the same day along with intervention groups. Safety outcomes were incidences and severity of adverse events occurred within 14 days after the third dose, as well as the association with the injection evaluated by investigators.

Human convalescent serum (HCS) samples were obtained from 35 people who had had a laboratory-confirmed COVID-19 diagnosis and had been recovered for at least 2 weeks as control. Serum samples were collected between 30-40 days since onset.

The severity of COVID-19 illness was all classified as mild-to-moderate. Most of the participants were females (n=22, 62.9%). The mean age among participants were 45.4 (SD 16.8) years.

Whole blood samples were subjected to Ficoll (Cytiva, 17-1440-03) gradient centrifugation after 1:1 dilution in PBS (Invitrogen, C10010500BT) + 2% FBS (Gibco, A3160901). After centrifugation, plasma was collected from the upper layer.

Authentic SARS-CoV-2 neutralization experiments were performed using CPE assay.

Serum/plasma samples were inactivated at 56℃ for 0.5h and serially diluted with cell culture medium in two-fold steps. The diluted plasma was mixed with a virus suspension of 100TCID50 in 96-well plates at a ratio of 1:1, followed by 2 hours incubation at 36.5°C in a 5% CO2 incubator. 1x10 4 Vero cells (ATCC, CCL-81) were then added to the serum-virus mixture, and the plates were incubated for 5 days at 36.5°C in a 5% CO2 incubator. The cytopathic effect (CPE) of each well was recorded under microscopes. Assays for each sample were replicated once and the neutralization titer was calculated by the Spearman-Karber method accounting for the previous 2-fold dilution during plasma collection. All experiments were performed in a Biosafety Level 3 laboratory.

ELISA plates were coated with 100 μL 1 μg/mL antigen protein (SARS-CoV-2 Spike protein) overnight (16~20 hours) at 2~8℃. Following three times of washing and blocking with 10% FBS in 0.01M PBS at 37℃ for 120 min, serially diluted serum samples were added to each well and incubated at 37℃ for 60 min. Then plates were washed three times and incubated with anti-IgG at 37℃ for 60 min. After five times of washing, substrate solution was added to each well and incubated for 15 minutes at room temperature, and then the stop solution buffer was added. Absorbance at 450 nm was measured. The positive sample is defined as the sample OD value ≥ 2.1 times of negative serum OD value. Endpoint titer was defined using the highest positive dilution-fold.

We assessed immunogenic endpoints at individual-level and group-level, respectively, which included participants who had both antibody results available according to the protocol at two visits and who had antibody results available at either of the two visits.

Safety assessment was performed in a safety population data set of all subjects who received the third dose.

The demographics of participants were summarized for intervention groups. Pearson χ² test or Fisher's exact test was used to analyze categorical outcomes. GMTs and corresponding 95% CIs were calculated based on the standard normal distribution of log-transformed antibody titers. Seroconversion rate and corresponding 95% CIs were derived from a binomial distribution. Pairwise comparisons were conducted by group t-tests, nonparametric Kruskal-Wallis H test, and Wilcoxon signed-rank test with logtransformation. Hypothesis testing was two-sided, and we considered p values of less than 0.05 to be significant. We used R software version 4.1.0 for all analyses. 

Interval between second and third doses (months) 4-5 CoronaVac