COVID-19 lateral flow IgG seropositivity and serum neutralising antibody responses after primary and booster vaccinations in Chile: a cross-sectional study.

By June 30, 2022, 92·6% of the Chilean population older than 18 years had received a full primary SARS-CoV-2 vaccine series, mostly with CoronaVac (Sinovac Biotech), and 78·4% had received a booster dose, mostly heterologous with BNT162b2 (Pfizer-BioNTech) and ChAdOx1 (AstraZeneca). We previously reported national seroprevalence data from lateral flow testing of IgG SARS-CoV-2 antibodies up to 16 weeks after primary vaccination. Our aim here was to study IgG seropositivity dynamics up to 30 weeks after primary vaccination and, in CoronaVac recipients, up to 26 weeks after booster vaccination, and to establish the correlation between lateral flow tests and neutralising antibody titres. In this cross-sectional study, testing stations for SARS-CoV-2 IgG detection were selected and installed from March 12, 2021, in hotspots in 24 large Chilean cities, and were maintained until March 31, 2022. Individuals voluntarily approaching the testing stations were invited to perform a rapid lateral flow test via a finger prick and complete a questionnaire. Between Aug 12, 2021, and April 1, 2022, volunteers seeking medical care in the Mutual de Seguridad de la Cámara Chilena de la Construcción provided blood samples for lateral flow testing and neutralising antibody studies; inclusion criteria were age at least 18 years, history of complete primary vaccination series with CoronaVac, BNT162b2, or ChAdOx1, or no vaccine, and no previous COVID-19 diagnosis. We tested the difference in IgG positivity across time, and between primary and booster doses, in all eligible participants with complete records, controlling for age, gender, and comorbidities. We also assessed the predictive power of neutralising antibody titres and sociodemographic characteristics on the probability of IgG positive results using multivariable logistic regression. Of 107 220 individuals recruited at the testing stations, 101 070 were included in our analysis (59 862 [59·2%] women and 41 208 [40·8%] men). 65 902 (65·2%) received primary vaccination series with CoronaVac, 18 548 (18·4%) with BNT162b2, and 606 (0·6%) with ChAdOx1, and 16 014 (15·8%) received no vaccine. Among the 61 767 individuals with a complete primary vaccination series with CoronaVac, 608 (1·0%) received a CoronaVac booster, 10 095 (16·3%) received a BNT162b2 booster, and 5435 (8·8%) received a ChAdOx1 booster. After ChAdOx1 primary vaccination, seropositivity peaked at week 5 after the second dose, occurring in 13 (92·9%, 95% CI 79·4-100·0) of 14 individuals. In participants who received a complete CoronaVac primary series, the decline in seropositivity stabilised at week 18 after the second dose (86 [44·7%, 95% CI 41·8-47·7] of 1087 individuals), whereas after receiving BNT162b2, seropositivity declined slightly by week 25 after the second dose (161 [94·2%, 90·6-97·7] of 171). A lower proportion of individuals who received the CoronaVac primary series and a homologous booster were seropositive (279 [85·6%, 95% CI 81·8-89·4] of 326) by weeks 2-18 than those who received a BNT162b2 booster (7031 [98·6%, 98·4-98·9] of 7128) or a ChAdOx1 booster (2893 [98·0%, 97·5-98·5] of 2953). The correlation between IgG positivity and log of the infectious dose in 50% of neutralising antibodies was moderate, with a sensitivity of 81·4% (95% CI 76·3-86·6) and specificity of 92·5% (73·3-100·0). Dynamic monitoring of IgG positivity to SARS-CoV-2 can characterise antibody waning over time in the absence or presence of booster doses, providing relevant data for the design of vaccination strategies. The correlation between lateral flow test IgG titres and neutralising antibody concentrations suggests that they could be a quick and effective surveillance tool to measure protection against SARS-CoV-2. Instituto Sistemas Complejos de Ingeniería, Subsecretaría de Redes Asistenciales, Ministry of Health, Chile, and Mutual de Seguridad de la Cámara Chilena de la Construcción.

Sauré D ，O'Ryan M ，Torres JP ，Zuñiga M ，Soto-Rifo R ，Valiente-Echeverría F ，Gaete-Argel A ，Neira I ，Saavedra V ，Acevedo ML ，Archila C ，Acuña F ，Rain M ，Basso LJ ... -  《Lancet Microbe》

Dynamic IgG seropositivity after rollout of CoronaVac and BNT162b2 COVID-19 vaccines in Chile: a sentinel surveillance study.

By July 14, 2021, 81·3 % of adults (aged ≥18 years) in Chile had received a first SARS-CoV-2 vaccine and 72·3% had received a second SARS-CoV-2 vaccine, with the majority of people given Sinovac's inactivated CoronaVac vaccine (75·3% of vaccines dispensed) or Pfizer-BioNTech's mRNA BNT162b2 vaccine (20·9% of vaccines dispensed). Due to the absence of simultaneous real-world data for these vaccines, we aimed to compare SARS-CoV-2 IgG positivity between vaccines using a dynamic national monitoring strategy. From March 12, 2021, 28 testing stations for SARS-CoV-2 IgG detection were installed in hotspots based on cellular-phone mobility tracking within the most populated cities in Chile. Individuals voluntarily approaching the testing stations were invited to do a lateral flow test by finger prick and respond to a questionnaire on sociodemographic characteristics, vaccination status (including type of vaccine if one was received), variables associated with SARS-CoV-2 exposure, and comorbidities. We compared the proportion of individuals testing positive for anti-SARS-CoV-2 IgG across sites by week since vaccination between recipients of CoronaVac and BNT162b2. Unvaccinated participants served as a control population and were matched to vaccinated individuals on the basis of date of presentation to the testing station, gender, and age group. Individuals were excluded from the analysis if they were younger than 18 years, had no declared gender, had an invalid IgG test result, had previously tested positive for SARS-CoV-2 infection on PCR, could not recall their vaccination status, or had been immunised against COVID-19 with vaccines other than CoronaVac or BNT162b2. Here, we report data collected up to July 2, 2021. Of 64 813 individuals enrolled, 56 261 were included in the final analysis, of whom 33 533 (59·6%) had received at least one dose of the CoronaVac vaccine, 8947 (15·9%) had received at least one dose of the BNT162b2 vaccine, and 13 781 (24·5%) had not received a vaccine. SARS-CoV-2 IgG positivity during week 4 after the first dose of CoronaVac was 28·1% (95% CI 25·0-31·2; 220 of 783 individuals), reaching a peak of 77·4% (75·5-79·3; 1473 of 1902 individuals) during week 3 after the second dose. SARS-CoV-2 IgG positivity during week 4 after the first dose of the BNT162b2 vaccine was 79·4% (75·7-83·1; 367 of 462 individuals), increasing to 96·5% (94·9-98·1; 497 of 515 individuals) during week 3 after the second dose and remaining above 92% until the end of the study. For unvaccinated individuals, IgG seropositivity ranged from 6·0% (4·4-7·6; 49 of 810 individuals) to 18·7% (12·5-24·9; 28 of 150 individuals) during the 5 month period. Regression analyses showed that IgG seropositivity was significantly lower in men than women and in people with diabetes or chronic diseases for CoronaVac vaccine recipients (p<0·0001), and for individuals aged 60 years and older compared with people aged 18-39 years for both vaccines (p<0·0001), 3-16 weeks after the second dose. IgG seropositivity was lower after CoronaVac than after BNT162b2 and declined over time since vaccination for CoronaVac recipients but not BNT162b2 recipients. Prolonged IgG monitoring will allow further evaluation of seropositivity overtime, providing data, in conjunction with effectiveness studies, for possible future re-assessment of vaccination strategies. Instituto Sistemas Complejos de Ingeniería and Ministerio de Salud Chile. For the Spanish translation of the abstract see Supplementary Materials section.

Sauré D ，O'Ryan M ，Torres JP ，Zuniga M ，Santelices E ，Basso LJ ... -  《-》

Heterologous versus homologous COVID-19 booster vaccination in previous recipients of two doses of CoronaVac COVID-19 vaccine in Brazil (RHH-001): a phase 4, non-inferiority, single blind, randomised study.

The inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac, Sinovac) has been widely used in a two-dose schedule. We assessed whether a third dose of the homologous or a different vaccine could boost immune responses. RHH-001 is a phase 4, participant masked, two centre, safety and immunogenicity study of Brazilian adults (18 years and older) in São Paulo or Salvador who had received two doses of CoronaVac 6 months previously. The third heterologous dose was of either a recombinant adenoviral vectored vaccine (Ad26.COV2-S, Janssen), an mRNA vaccine (BNT162b2, Pfizer-BioNTech), or a recombinant adenoviral-vectored ChAdOx1 nCoV-19 vaccine (AZD1222, AstraZeneca), compared with a third homologous dose of CoronaVac. Participants were randomly assigned (5:6:5:5) by a RedCAP computer randomisation system stratified by site, age group (18-60 years or 61 years and over), and day of randomisation, with a block size of 42. The primary outcome was non-inferiority of anti-spike IgG antibodies 28 days after the booster dose in the heterologous boost groups compared with homologous regimen, using a non-inferiority margin for the geometric mean ratio (heterologous vs homologous) of 0·67. Secondary outcomes included neutralising antibody titres at day 28, local and systemic reactogenicity profiles, adverse events, and serious adverse events. This study was registered with Registro Brasileiro de Ensaios Clínicos, number RBR-9nn3scw. Between Aug 16, and Sept 1, 2021, 1240 participants were randomly assigned to one of the four groups, of whom 1239 were vaccinated and 1205 were eligible for inclusion in the primary analysis. Antibody concentrations were low before administration of a booster dose with detectable neutralising antibodies of 20·4% (95% CI 12·8-30·1) in adults aged 18-60 years and 8·9% (4·2-16·2) in adults 61 years or older. From baseline to day 28 after the booster vaccine, all groups had a substantial rise in IgG antibody concentrations: the geometric fold-rise was 77 (95% CI 67-88) for Ad26.COV2-S, 152 (134-173) for BNT162b2, 90 (77-104) for ChAdOx1 nCoV-19, and 12 (11-14) for CoronaVac. All heterologous regimens had anti-spike IgG responses at day 28 that were superior to homologous booster responses: geometric mean ratios (heterologous vs homologous) were 6·7 (95% CI 5·8-7·7) for Ad26.COV2-S, 13·4 (11·6-15·3) for BNT162b2, and 7·0 (6·1-8·1) for ChAdOx1 nCoV-19. All heterologous boost regimens induced high concentrations of pseudovirus neutralising antibodies. At day 28, all groups except for the homologous boost in the older adults reached 100% seropositivity: geometric mean ratios (heterologous vs homologous) were 8·7 (95% CI 5·9-12·9) for Ad26.COV2-S vaccine, 21·5 (14·5-31·9) for BNT162b2, and 10·6 (7·2-15·6) for ChAdOx1 nCoV-19. Live virus neutralising antibodies were also boosted against delta (B.1.617.2) and omicron variants (B.1.1.529). There were five serious adverse events. Three of which were considered possibly related to the vaccine received: one in the BNT162b2 group and two in the Ad26.COV2-S group. All participants recovered and were discharged home. Antibody concentrations were low at 6 months after previous immunisation with two doses of CoronaVac. However, all four vaccines administered as a third dose induced a significant increase in binding and neutralising antibodies, which could improve protection against infection. Heterologous boosting resulted in more robust immune responses than homologous boosting and might enhance protection. Ministry of Health, Brazil.

Costa Clemens SA ，Weckx L ，Clemens R ，Almeida Mendes AV ，Ramos Souza A ，Silveira MBV ，da Guarda SNF ，de Nobrega MM ，de Moraes Pinto MI ，Gonzalez IGS ，Salvador N ，Franco MM ，de Avila Mendonça RN ，Queiroz Oliveira IS ，de Freitas Souza BS ，Fraga M ，Aley P ，Bibi S ，Cantrell L ，Dejnirattisai W ，Liu X ，Mongkolsapaya J ，Supasa P ，Screaton GR ，Lambe T ，Voysey M ，Pollard AJ ，RHH-001 study team ... -  《-》

Comparison of SARS-CoV-2 anti-spike receptor binding domain IgG antibody responses after CoronaVac, BNT162b2, ChAdOx1 COVID-19 vaccines, and a single booster dose: a prospective, longitudinal population-based study.

Vaccination is an efficient strategy to control the COVID-19 pandemic. In north Cyprus, vaccine distribution started with CoronaVac followed by BNT162b2, and ChAdOx1 vaccines. An option to obtain a third booster dose with BNT162b2 or CoronaVac was later offered to people fully inoculated with CoronaVac. There are few simultaneous and comparative real-world antibody data for these three vaccines as well as boosters after CoronaVac vaccination. Our study was aimed at evaluating antibody responses after these vaccination schemes. We did a prospective, longitudinal population-based study to measure SARS-CoV-2 anti-spike receptor binding domain (RBD) IgG concentrations, assessed by assaying blood samples collected, in participants in north Cyprus who had received the BNT162b2, ChAdOx1, or CoronaVac vaccine at 1 month and 3 months after the second dose. Participants were recruited when they voluntarily came to the laboratory for testing after vaccination, solicited from health-care access points, or from the general population. We also evaluated antibody responses 1 month after a booster dose of BNT162b2 or CoronaVac after primary CoronaVac regimen. Demographics, baseline characteristics, vaccination reactions, and percentage of antibody responders were collected by phone interviews or directly from the laboratory summarised by vaccine and age group. Antibody levels were compared between groups over time by parametric and non-parametric methods. Recruitment, follow-up, and data collection was done between March 1 and Sept 30, 2021. BNT162b2 induced the highest seropositivity and anti-spike RBD IgG antibody titres, followed by ChAdOx1, and then by CoronaVac. In addition, the rate of decline of antibodies was fastest with CoronaVac, followed by ChAdOx1, and then by BNT162b2. For the older age group, the rate of seropositivity at 3 months after the second dose was 100% for BNT162b2, 90% for ChAdOx1, and 60% for CoronaVac. In the multivariate repeated measures model, lower antibody titres were also significantly associated with male sex, older age, and time since vaccination. Boosting a two-dose CoronaVac regimen at 6 months with a single BNT162b2 dose led to significantly increased titres of IgG compared with boosting with CoronaVac; for the 60 years and older age group, the geometric mean fold rise in antibody titre after the booster relative to 1 month post-baseline was 7·9 (95% CI 5·8-10·8) in the BNT162b2 boost group versus 2·8 (1·6-5·0) in the CoronaVac group. These longitudinal data can help shape vaccination strategies. Given the low antibody titres and fast decline in the CoronaVac group in individuals 60 years or older, more potent vaccine options could be considered as the primary vaccination or booster dose in these high-risk populations to sustain antibody responses for longer. Crowdfunded in north Cyprus.

Barin B ，Kasap U ，Selçuk F ，Volkan E ，Uluçkan Ö ... -  《Lancet Microbe》

Immunogenicity and safety in healthy adults of full dose versus half doses of COVID-19 vaccine (ChAdOx1-S or BNT162b2) or full-dose CoronaVac administered as a booster dose after priming with CoronaVac: a randomised, observer-masked, controlled trial in I

Inactivated COVID-19 vaccines effectively prevent death, but their effectiveness for preventing infection or severe illness is known to decrease within 3-6 months following the second priming dose. Here we aimed to evaluate the immunogenicity and safety of three potential booster vaccines administered as a full-dose homologous booster or full-dose or half-dose heterologous boosters among individuals primed with CoronaVac. We did an observer and participant masked, randomised controlled trial study of healthy Indonesian adults from five recruitment sites in Bandung and Jakarta, Indonesia, aged 18 years and older who had previously received two doses of CoronaVac within 3 to less than 6 months or 6 to 9 months before the booster dose. Participants were randomly assigned (1:1:1:1:1) by means of stratified randomisation with random block size to a homologous booster with full-dose CoronaVac or heterologous boosters with ChAdOx1-S or BNT162b2 in full dose or half dose. The primary outcome was to evaluate the seropositive, seroconversion rate, and the geometric mean titres of IgG anti-spike-receptor binding domain and neutralising antibodies, 28 days after booster dose vaccination in the per-protocol population. Safety was assessed as a secondary outcome in all vaccinated booster participants by the incidence rate and intensity of adverse events within 24 h, 7 days, and 28 days after the booster dose. This study is registered with ina-registry.org, INA-GO0HLGB, and is complete. Between Nov 26 and Dec 16, 2021, 1015 people were screened, and 960 healthy adults were enrolled; 190-193 were included in each group. 28 days after receiving the booster, combining the 3 to less than 6 months and 6 to 9 months groups, the proportions of seroconversion rates in each vaccine group were ChAdOx1-S 75 (82%) of 92 to 87 (88%) of 99 for full dose and half dose, BNT162b2 92 (92%) of 100 to 90 (98%) of 92 for full dose and half dose, and CoronaVac in 38 (41%) of 92 to 65 (66%) of 98. All booster groups achieved 100% seropositivity 28 days after the booster dose. Participants in the 6 to 9 months priming group achieved higher titres compared with participants in the 3 to less than 6 months priming group. The geometric mean titres in participants in the 6 to 9 months priming group in each vaccine group were ChAdOx1-S 11258·69 (9562·43-13 255·85) and 7853·04 (6698·92-9206·00) for full dose and half dose, BNT162b2 19999·84 (17 720·58-22 572·25) and 17 017·62 (14 694·40-19 708·16) for full dose and half dose and CoronaVac 1440·55 (1172·81-1769·42) achieved higher titres compared with participants in the 3 to less than 6 months priming group which in each vaccine group were ChAdOx1-S 7730·39 (6401·87-9334·60) and 6684·34 (5678·94-7867·73) for full dose and half dose, BNT162b2 16594·08 (13 993·08-19 678·55) and 12 121·67 (9925·21-14 804·19) for full dose and half dose, and CoronaVac 1210·23 (976·49-1499·92). The median percentage inhibition for the surrogate virus neutralisation test against the delta B.1.617.2 and wild-type (WT) variant before the booster and 28 days after the booster dose was very high in all groups (p<0·001), all with greater than 90% inhibition against both delta and WT strains. No serious adverse events were associated with the vaccines. Within the heterologous booster groups, the adverse event rates in the half-dose groups were lower compared with the full-dose groups. Geometric mean titre values between participants in the 6 to 9 months priming group and the 3 to less than 6 months priming group before the booster dose and between half-dose and full-dose groups 28 days before the booster were not significantly different for half-dose ChAdOx1-S, full-dose BNT162b2, and CoronaVac and were significantly different for full-dose ChAdOx1-S and half-dose BNT162b2. Among individuals primed with CoronaVac, boosting with BNT162b2 (full dose or half dose) or ChAdOx1-S (full dose or half dose) produces substantially better immune responses than in those boosted with CoronaVac. Full-dose and half-dose boosting with either BNT162b2 or ChAdOx1-S produced similar responses. Heterologous booster with half-dose might be considered in adults primed with two doses of CoronaVac vaccine. Ministry of Health, Indonesia. For the Indonesian translation of the abstract see Supplementary Materials section.

Fadlyana E ，Setiabudi D ，Kartasasmita CB ，Putri ND ，Rezeki Hadinegoro S ，Mulholland K ，BCOV21 study group ... -  《-》