Trends of humoral immune responses to heterologous antigenic exposure due to vaccination & omicron SARS-CoV-2 infection: Implications for boosting

Background & objectives

Vaccination and natural infection can both augment the immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but how omicron infection has affected the vaccine-induced and hybrid immunity is not well studied in Indian population. The present study was aimed to assess the durability and change in responses of humoral immunity with age, prior natural infection, vaccine type and duration with a minimum gap of six months post-two doses with either ChAdOx1 nCov-19 or BBV152 prior- and post-emergence of the omicron variant.

Methods

A total of 1300 participants were included in this observational study between November 2021 and May 2022. Participants had completed at least six months after vaccination (2 doses) with either ChAdOx1 nCoV-19 or an inactivated whole virus vaccine BBV152. They were grouped according to their age (≤ or ≥60 yr) and prior exposure of SARS-CoV-2 infection. Five hundred and sixteen of these participants were followed up after emergence of the Omicron variant. The main outcome was durability and augmentation of the humoral immune response as determined by anti-receptor-binding domain (RBD) immunoglobulin G (IgG) concentrations, anti-nucleocapsid antibodies and anti-omicron RBD antibodies. Live virus neutralization assay was conducted for neutralizing antibodies against four variants - ancestral, delta and omicron and omicron sublineage BA.5.

Results

Before the omicron surge, serum anti-RBD IgG antibodies were detected in 87 per cent participants after a median gap of eight months from the second vaccine dose, with a median titre of 114 [interquartile range (IQR) 32, 302] BAU/ml. The levels increased to 594 (252, 1230) BAU/ml post-omicron surge (P<0.001) with 97 per cent participants having detectable antibodies, although only 40 had symptomatic infection during the omicron surge irrespective of vaccine type and previous history of infection. Those with prior natural infection and vaccination had higher anti-RBD IgG titre at baseline, which increased further [352 (IQR 131, 869) to 816 (IQR 383, 2001) BAU/ml] (P<0.001). The antibody levels remained elevated after a mean time gap of 10 months, although there was a decline of 41 per cent. The geometric mean titre was 452.54, 172.80, 83.1 and 76.99 against the ancestral, delta, omicron and omicron BA.5 variants in the live virus neutralization assay.

Interpretation & conclusions

Anti-RBD IgG antibodies were detected in 85 per cent of participants after a median gap of eight months following the second vaccine dose. Omicron infection probably resulted in a substantial proportion of asymptomatic infection in the first four months in our study population and boosted the vaccine-induced humoral immune response, which declined but still remained durable over 10 months.

Immunogenicity and safety of homologous and heterologous booster vaccination of ChAdOx1 nCoV-19 (COVISHIELD™) and BBV152 (COVAXIN®): a non-inferiority phase 4, participant and observer-blinded, randomised study

Background

Primary SARS-CoV-2 vaccination has been shown to wane with time and provide lower protection from disease with new viral variants, prompting the WHO to recommend the administration of booster doses. We determined the safety and immunogenicity of homologous or heterologous boosters with ChAdOx1 nCoV-19 (COVISHIELD™) or BBV152 (COVAXIN®), the two vaccines used widely for primary immunization in India, in participants who had already received two primary doses of these vaccines.

Methods

Participants primed with two doses each of COVISHIELD™ or COVAXIN® 12-36 weeks previously, were randomised to receive either COVISHIELD™ or COVAXIN® booster in a 1:1 ratio. The primary outcome was day 28 post-booster anti-spike IgG seropositivity and secondary outcomes were anti-spike IgG levels and assessment of safety and reactogenicity. The results of 90 days intention-to-treat analysis are presented. This trial is registered with ISRCTN (CTRI/2021/08/035648).

Findings

In the COVISHIELD™ primed group with 200 participants, the seropositivity 28 days post booster in the heterologous COVAXIN® arm was 99% and non-inferior to the homologous COVISHIELD™ arm, which was also 99% (difference 0%; 95% CI: -2.8% to 2.7%). The geometric mean concentration (GMC) of anti-spike antibodies following heterologous COVAXIN® boost on day 28 was 36,190.78 AU/mL (95% CI: 30,526.64-42,905.88) while the GMC following homologous COVISHIELD™ boost was 97,445.09 AU/mL (82,626.97-114,920.7). In the COVAXIN® primed group with 204 participants, the seropositivity 28 days post booster in the heterologous COVISHIELD™ arm was 100% and non inferior to the homologous COVAXIN® arm which was 96% (difference 4%, 95% CI: 0.2%-7.8%). The GMC following heterologous COVISHIELD™ boost was 241,681.6 AU/mL (95% CI: 201,380.2-290,048.3) compared to homologous COVAXIN® boost, which was 48,473.94 AU/mL (95% CI: 38,529.56-60,984.95). The day 28 geometric mean ratio (GMR) of the anti-spike IgG between the heterologous and homologous boosted arms was 0.42 (95% CI: 0.34-0.52) in the COVISHIELD™ primed group and 5.11 (95% CI: 3.83-6.81) in the COVAXIN® primed group. There were no related serious adverse events reported in any group.

Interpretation

Homologous and heterologous boosting with COVISHIELD™ or COVAXIN® in COVISHIELD™ or COVAXIN® primed individuals are immunogenic and safe. A heterologous boost with COVISHIELD™ after COVAXIN® prime offers the best immune response among the four combinations evaluated.

Funding

Azim Premji Foundation and Bill and Melinda Gates Foundation.

Host immune responses in aged rhesus macaques against BBV152, an inactivated SARS-CoV-2 vaccine, and cross-neutralization with beta and delta variants

The magnitude and duration of immune response to COVID-19 vaccination in older adults are known to be adversely affected due to immunosenescence and inflammaging. The threat of emerging variants warrants studies on immune response in older adults to primary vaccination and booster doses so as to understand the effectiveness of vaccines in countering the threat of emerging variants. Non-human primates (NHPs) are ideal translational models, as the immunological responses in NHPs are similar to those in humans, so it enables us to understand host immune responses to the vaccine. We initially studied humoral immune responses in aged rhesus macaques employing a three-dose regimen of BBV152, an inactivated SARS-CoV-2 vaccine. Initially, the study investigated whether the third dose enhances the neutralizing antibody (Nab) titer against the homologous virus strain (B.1) and variants of concern (Beta and Delta variants) in aged rhesus macaques immunized with BBV152, adjuvanted with Algel/Algel-IMDG (imidazoquinoline). Later, we also attempted to understand cellular immunity in terms of lymphoproliferation against γ-inactivated SARS-CoV-2 B.1 and delta in naïve and vaccinated rhesus macaques after a year of the third dose. Following the three-dose regimen with 6 µg of BBV152 with Algel-IMDG, animals had increased Nab responses across all SARS-CoV-2 variants studied, which suggested the importance of booster dose for the enhanced immune response against SARS-CoV-2-circulating variants. The study also revealed the pronounced cellular immunity against B.1 and delta variants of SARS-CoV-2 in the aged rhesus macaques even after a year of vaccination.

Demographics and Clinical Characteristics of COVID-19-vaccinated Patients Admitted to ICU: A Multicenter Cohort Study from India (PostCoVac Study-COVID Group)

Background

Emergency authorization and approval were given for the coronavirus disease-19 (COVID-19) vaccines. The efficacy reported after phase III trials were 70.4% and 78% for Covishield and Covaxin, respectively.In this study, we aim to analyze the risk factors, which were associated with mortality in critically ill COVID-19-vaccinated patients admitted into intensive care unit (ICU).

Materials and methods

This study was conducted from April 1, 2021 to December 31, 2021 across five centers in India. Patients who had received either one or two doses of any of the COVID vaccines and developed COVID-19 were included. The ICU mortality was a primary outcome.

Results

A total of 174 patients with COVID-19 illness were included in the study. The mean age was 57 years standard deviation (SD 15). Acute physiology, age and chronic health evaluation (APACHE II) score and the sequential organ failure assessment (SOFA) score were 14 (8-24.5) and 6 (4-8), respectively. Multiple variable logistic regression showed patients who have received a single dose [odds ratio (OR): 2.89, confidence interval (CI): 1.18, 7.08], neutrophil:lymphocyte (NL) ratio (OR: 1.07, CI: 1.02,1.11), and SOFA score (OR: 1.18, CI: 1.03,1.36) were associated with higher mortality.

Conclusion

The mortality in the vaccinated patients admitted to the ICU was 43.68% due to COVID illness. The mortality was lower in patients who had received two doses.

How to cite this article

Havaldar AA, Prakash J, Kumar S, Sheshala K, Chennabasappa A, Thomas RR et al. Demographics and Clinical Characteristics of COVID-19-vaccinated Patients Admitted to ICU: A Multicenter Cohort Study from India (PostCoVac Study-COVID Group). Indian J Crit Care Med 2022;26(11):1184-1191.

Low SARS-CoV-2 viral load among vaccinated individuals infected with Delta B.1.617.2 and Omicron BA.1.1.529 but not with Omicron BA.1.1 and BA.2 variants

The rapid spread of SARS-CoV-2 variants in the global population is indicative of the development of selective advantages in emerging virus strains. Here, we performed a case-control investigation of the clinical and demographic characteristics, clinical history, and virological markers to predict disease progression in hospitalized adults for COVID-19 between December 2021 and January 2022 in Chennai, India. COVID-19 diagnosis was made by a commercial TaqPath COVID-19 RT-PCR, and WGS was performed with the Ion Torrent Next Generation Sequencing System. High-quality (<5% of N) complete sequences of 73 Omicron B.1.1.529 variants were randomly selected for phylogenetic analysis. SARS-CoV-2 viral load, number of comorbidities, and severe disease presentation were independently associated with a shorter time-to-death. Strikingly, this was observed among individuals infected with Omicron BA.2 but not among those with the BA.1.1.529, BA.1.1, or the Delta B.1.617.2 variants. Phylogenetic analysis revealed severe cases predominantly clustering under the BA.2 lineage. Sequence analyses showed 30 mutation sites in BA.1.1.529 and 33 in BA.1.1. The mutations unique to BA.2 were T19I, L24S, P25del, P26del, A27S, V213G, T376A, D405N and R408S. Low SARS-CoV-2 viral load among vaccinated individuals infected with Delta B.1.617.2 and the Omicron BA.1.1.529 variant but not with Omicron BA.1.1 or BA.2 suggests that the newer strains are largely immune escape variants. The number of vaccine doses received was independently associated with increased odds of developing asymptomatic disease or recovery. We propose that the novel mutations reported herein could likely bear a significant impact on the clinical characteristics, disease progression, and epidemiological aspects of COVID-19. Surging rates of mutations and the emergence of eclectic variants of SARS-CoV-2 appear to impact disease dynamics.

Inactivated vaccine Covaxin/BBV152: A systematic review

We systematically reviewed and summarized studies focusing on Bharat Biotech’s Whole Virion Inactivated Corona Virus Antigen BBV152 (Covaxin), which is India’s indigenous response to fighting the SARS-CoV-2 pandemic. Studies were searched for data on the efficacy, immunogenicity, and safety profile of BBV152. All relevant studies published up to March 22, 2022, were screened from major databases, and 25 studies were eventually inducted into the systematic review. The studies focused on the virus antigen (6 μg) adjuvanted with aluminium hydroxide gel and/or Imidazo quinolin gallamide (IMDG), aTLR7/8 agonist. Pre-clinical, phase I, and II clinical trials showed appreciable immunogenicity. Both neutralizing and binding antibody titers were significant and T cell responses were Th1-biased. Phase III trials on the 6 μg +Algel-IMDG formulation showed a 93.4% efficacy against severe COVID-19. Data from the trials revealed an acceptable safety profile with mostly mild-moderate local and systemic adverse events. No serious adverse events or fatalities were seen, and most studies reported milder and lesser adverse events with Covaxin when compared with other vaccines, especially Oxford-Astra Zeneca’s AZD1222 (Covishield). The immunogenicity performance of Covaxin, which provided significant protection only after the second dose, was mediocre and it was consistently surpassed by Covishield. One study reported adjusted effectiveness against symptomatic infection to be just 50% at 2 weeks after the second dose. Nonetheless, appreciable results were seen in previously infected individuals administered both doses. There was some evidence of coverage against the Alpha, Beta, and Delta variants. However, neither Covaxin nor Covishield showed sufficient protection against the Omicron variant. Two studies reported super-additive results on mixing Covaxin with Covishield. Further exploration of heterologous prime-boost vaccination with a combination of an inactivated vaccine and an adenoviral vector-based vaccine for tackling future variants may be beneficial.

Clinical profile of ChAdOx1 nCoV-19- and BBV152-vaccinated individuals among hospitalized COVID-19 patients: a pair-matched study

Background:

COVID-19 infections among severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-vaccinated individuals are of clinical concern, especially in those requiring hospitalization. Such real-world data on ChAdOx1 nCoV-19- and BBV152-vaccinated individuals are scarce. Hence, there is an urgent need to understand their clinical profile and outcomes.

Methods:

A 1:1 pair-matched study was performed among vaccinated and unvaccinated COVID-19 patients admitted between March 2021 and June 2021 at a tertiary care centre in New Delhi, India. The vaccinated group (received at least one dose of ChAdOx1 nCoV-19 or BBV152) was prospectively followed till discharge or death and matched [for age (±10 years), sex, baseline disease severity and comorbidities] with a retrospective group of unvaccinated patients admitted during the study period. Paired analysis was done to look for clinical outcomes between the two groups.

Results:

The study included a total of 210 patients, with 105 in each of the vaccinated and unvaccinated groups. In the vaccinated group, 47 (44.8%) and 58 (55.2%) patients had received ChAdOx1 nCoV-19 and BBV152, respectively. However, 73 patients had received one dose and 32 had received two doses of the vaccine. Disease severity was mild in 36.2%, moderate in 31.4% and severe in 32.4%. Two mortalities were reported out of 19 fully vaccinated individuals. All-cause mortality in the vaccinated group was 8.6% (9/105), which was significantly lower than the matched unvaccinated group mortality of 21.9% (23/105), p = 0.007. Vaccination increased the chances of survival (OR = 3.8, 95% CI: 1.42–10.18) compared to the unvaccinated group.

Conclusion:

In the second wave of the pandemic predominated by delta variant of SARS CoV-2, vaccination reduced all-cause mortality among hospitalized patients, although the results are only preliminary.

A machine learning-based approach to determine infection status in recipients of BBV152 (Covaxin) whole-virion inactivated SARS-CoV-2 vaccine for serological surveys

Data science has been an invaluable part of the COVID-19 pandemic response with multiple applications, ranging from tracking viral evolution to understanding the vaccine effectiveness. Asymptomatic breakthrough infections have been a major problem in assessing vaccine effectiveness in populations globally. Serological discrimination of vaccine response from infection has so far been limited to Spike protein vaccines since whole virion vaccines generate antibodies against all the viral proteins. Here, we show how a statistical and machine learning (ML) based approach can be used to discriminate between SARS-CoV-2 infection and immune response to an inactivated whole virion vaccine (BBV152, Covaxin). For this, we assessed serial data on antibodies against Spike and Nucleocapsid antigens, along with age, sex, number of doses taken, and days since last dose, for 1823 Covaxin recipients. An ensemble ML model, incorporating a consensus clustering approach alongside the support vector machine model, was built on 1063 samples where reliable qualifying data existed, and then applied to the entire dataset. Of 1448 self-reported negative subjects, our ensemble ML model classified 724 to be infected. For method validation, we determined the relative ability of a random subset of samples to neutralize Delta versus wild-type strain using a surrogate neutralization assay. We worked on the premise that antibodies generated by a whole virion vaccine would neutralize wild type more efficiently than delta strain. In 100 of 156 samples, where ML prediction differed from self-reported uninfected status, neutralization against Delta strain was more effective, indicating infection. We found 71.8% subjects predicted to be infected during the surge, which is concordant with the percentage of sequences classified as Delta (75.6%-80.2%) over the same period. Our approach will help in real-world vaccine effectiveness assessments where whole virion vaccines are commonly used.

Factors Associated With the Decay of Anti-SARS-CoV-2 S1 IgG Antibodies Among Recipients of an Adenoviral Vector-Based AZD1222 and a Whole-Virion Inactivated BBV152 Vaccine

Background

The magnitude of protection conferred following recovery from COVID-19 or by vaccine administration, and the duration of protective immunity developed, remains ambiguous.

Methods

We investigated the factors associated with anti-SARS-CoV-2 S1 IgG decay in 519 individuals who recovered from COVID-19 illness or received COVID-19 vaccination with two commercial vaccines, viz., an adenoviral vector-based (AZD1222) and a whole-virion-based inactivated (BBV152) vaccine in Chennai, India from March to December 2021. Blood samples collected during regular follow-up post-infection/-vaccination were examined for anti-SARS-CoV-2 S1 IgG by a commercial automated chemiluminescent immunoassay (CLIA).

Results

Age and underlying comorbidities were the two variables that were independently associated with the development of a breakthrough infection. Individuals who were >60 years of age with underlying comorbid conditions (viz., hypertension, diabetes mellitus and cardiovascular disease) had a ~15 times and ~10 times greater odds for developing a breakthrough infection and hospitalization, respectively. The time elapsed since the first booster dose was associated with attrition in anti-SARS-CoV-2 IgG, where each month passed was associated with an ebb in the anti-SARS-CoV-2 IgG antibody levels by a coefficient of -6 units.

Conclusions

Our findings advocate that the elderly with underlying comorbidities be administered with appropriate number of booster doses with AZD1222 and BBV152 against COVID-19.

Sub-optimal neutralisation of omicron (B.1.1.529) variant by antibodies induced by vaccine alone or SARS-CoV-2 Infection plus vaccine (hybrid immunity) post 6-months

BACKGROUND

Rapid spread of the omicron SARS-CoV-2 variant despite extensive vaccination suggests immune escape. The neutralising ability of different vaccines alone or with natural SARS-CoV-2 infection against omicron is not well-known.

METHODS

In this cross-sectional study, we tested the ability of vaccine and natural infection induced antibodies to neutralise omicron variant in a live virus neutralisation assay in four groups of individuals: (i) ChAdOx1 nCoV-19 vaccination, (ii) ChAdOx1 nCoV-19 vaccination plus prior SARS-CoV-2 infection, (iii) vaccination with inactivated virus vaccine (BBV152), and (iv) BBV152 vaccination plus prior SARS-CoV-2 infection. Primary outcome was fold-change in virus neutralisation titre against omicron compared with ancestral virus.

FINDINGS

We included 80 subjects. The geometric mean titre (GMT) of the 50% focus reduction neutralisation test (FRNT50) was 380·4 (95% CI: 221·1, 654·7) against the ancestral virus with BBV152 vaccination and 379·3 (95% CI: 185·6, 775·2) with ChAdOx1 nCov-19 vaccination alone. GMT for vaccination plus infection groups were 806·1 (95% CI: 478·5, 1357·8) and 1526·2 (95% CI: 853·2, 2730·0), respectively. Against omicron variant, only 5 out of 20 in both BBV152 and ChAdOx1 nCoV-19 vaccine only groups, 6 out of 20 in BBV152 plus prior SARS-CoV-2 infection group, and 9 out of 20 in ChAdOx1 nCoV-19 plus prior SARS-CoV-2 infection group exhibited neutralisation titres above the lower limit of quantification (1:20) suggesting better neutralisation with prior infection. A reduction of 26·6 and 25·7 fold in FRNT50 titres against Omicron compared to ancestral SARS-CoV-2 strain was observed for individuals without prior SARS-CoV-2 infection vaccinated with BBV152 and ChAdOx1 nCoV-19, respectively. The corresponding reduction was 57·1 and 58·1 fold, respectively, for vaccinated individuals with prior infection. The 50% neutralisation titre against omicron demonstrated moderate correlation with serum anti-RBD IgG levels [Spearman r: 0·58 (0·41, 0·71)].

INTERPRETATION

Significant reduction in the neutralising ability of both vaccine-induced and vaccine plus infection-induced antibodies was observed for omicron variant which might explain immune escape.

FUNDING

Department of Biotechnology, India; Bill & Melinda Gates Foundation, USA.

Incidence and severity of COVID-19 infection post-vaccination: a survey among Indian doctors

Purpose

The rollout of COVID-19 vaccines began in India in January 2021, with healthcare professionals being the first to receive vaccination. The purpose of this research was to study the incidence and severity of COVID-19 infections among Indian doctors, following vaccination with ChAdOx1 nCoV-19 or BBV152.

Methods

We conducted an online voluntary survey among Indian doctors who received one or two doses of ChAdOx1 nCoV-19 or BBV152. Questions pertaining to the incidence and severity of COVID-19 infection following vaccination were asked. Data thus obtained were analysed.

Results

9146 doctors were included in this study. 8301 of these received ChAdOx1 nCoV-19, while 845 received BBV152. 2842 (31.07%) respondents reported having a COVID-19 infection following vaccination. Presence of pre-existing medical comorbidities was associated with a higher incidence, while prior COVID-19 infection and two doses of either vaccine were associated with a lower incidence of COVID-19 infection post-vaccination. Exposure to COVID-19 patients on a daily basis did not increase the incidence of COVID-19 infection among doctors who were vaccinated. Increasing age, male gender, presence of pre-existing medical comorbidities, and daily exposure to COVID-19 patients were associated with increased severity of COVID-19 infection after vaccination. Two doses of either vaccine resulted in less severity of disease compared to one dose.

Conclusion

ChAdOx1 nCoV-19 and BBV152 confer immunity against severe forms of COVID-19 infections. COVID-19 infections prior to vaccination result in a lower incidence of breakthrough infection. Presence of pre-existing medical comorbidities is associated with increased incidence and severity of breakthrough infections.

Antibody profile in post-vaccinated & SARS-CoV-2 infected individuals

Background & objectives

During the COVID-19 pandemic it was important to assess the antibody profile in individuals vaccinated with Covaxin (BBV152) and Covishield (ChAdOx1 nCoV-19) with both 28 and 84 days gaps between two doses, those infected with SARS-CoV-2 and post-COVID-19-infected individuals vaccinated with only one dose of either of the vaccines. The present study was aimed to assess these objectives.

Methods

Fifty real time reverse transcription-polymerase chain reaction (qRT-PCR)-confirmed COVID-19-infected individuals, along with 90 COVID-19-naïve (BBV152 and ChAdOx1 nCov-19)-vaccinated individuals, were included in the study. Individuals who received a single dose of either vaccine with a confirmed past diagnosis of SARS-CoV-2 infection (n=15) were also included. Blood samples were collected strictly between the 4^th and 5^th wk after development of symptoms for SARS-CoV-2 infected individuals and after the first/second vaccination dose. Antibody profile assessment was done using whole-virus, spike-receptor binding domain (RBD) and nucleocapsid-specific ELISA kits along with neutralizing antibody kit.

Results

There was an overall 97.7 per cent seropositivity rate in vaccinated individuals, and a strong correlation (R²=0.8, P<0.001) between neutralizing and spike-RBD antibodies. Among individuals who received two standard doses of ChAdOx1 nCoV-19 vaccine, the spike antibody levels developed were of higher titre with a longer prime boost interval than in those with shorter intervals (P<0.01). Individuals vaccinated with two doses as well as only one dose post-SARS-CoV-2 infection had high neutralizing and spike-specific antibodies.

Interpretation & conclusions

High neutralizing and spike-specific antibodies were developed in individuals vaccinated only with one dose of either vaccine post-SARS-CoV-2 infection. With the main priority being vaccinating majority of the population in our country, single-dose administration to such individuals would be a sensible way to make the most of the limited supplies. Furthermore, neutralizing antibody levels observed in COVID-19-naïve vaccinees imply the need for booster vaccination.

Comparable neutralization of SARS-CoV-2 Delta AY.1 and Delta with individuals sera vaccinated with BBV152

Sera of COVID-19 naive vaccinees, COVID-19 recovered cases with vaccination and breakthrough cases demonstrated 1.3, 2.5 and 1.9-fold reduction in neutralization titers against Delta and 1.5, 3.5, 2.8-fold against Delta AY.1 compared to B.1 respectively. However, high neutralization titers would still effectively protect against Delta, Delta AY.1 and B.1.617.3 variants.

Covaxin: An overview of its immunogenicity and safety trials in India

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to a global coronavirus disease-19 (COVID-19) pandemic. Several vaccine types, such as inactivated, viral vector-, or mRNA-based, have received approval against SARS-CoV-2. The ability to induceT-helper-1 cell (Th1) responses is desirable from an effective vaccine against this virus. Covaxin (BBV152) is a wholevirion inactivated SARS-CoV-2 vaccine adjuvanted with Algel-Imidazoquinoline (IMDG) molecule, a toll-like receptor (TLR) 7/8 agonist. The mRNA-based vaccine use is hindered because of cold storage requirement, whereas covaxin is stored between 2°C and 8°C, making it suitable for countries with limited resources. The Drug Controller General of India (DCGI) has approved the BBV152 vaccine. Therefore, it is of interest to document known data on BBV152 vaccine phase I, phase II and phase III human clinical trials to evaluate the safety, reactogenicity, tolerance, and immunogenicity of the whole-virion inactivated SARS-CoV-2 vaccine (BBV152).

Antibody responses to the BBV152 vaccine in individuals previously infected with SARS-CoV-2: A pilot study

Background & objectives

Vaccination against SARS-CoV-2 is a recommendation from the World Health Organization as the foremost preference in the current situation to control the COVID-19 pandemic. BBV152 is one of the approved vaccines against SARS-CoV-2 in India. In this study, we determined SARS-CoV-2-specific antibody levels at day 0 (baseline, before vaccination), day 28 ± 2 post-first dose (month 1) and day 56 ± 2 post-first dose (month 2) of BBV152 whole-virion-inactivated SARS-CoV-2 recipients, and compared the antibody responses of individuals with confirmed pre-vaccination SARS-CoV-2 infection to those individuals without prior evidence of infection.

Methods

Blood samples were collected from 114 healthcare professionals and frontline workers who received BBV152 vaccine from February to May & June 2021. Prior infection with SARS-CoV-2 was determined at baseline. Serum samples were used to estimate SARS-CoV-2 nucleoprotein-specific IgG [IgG (N)], spike protein-specific IgG [IgG (S)] and neutralizing antibodies (NAb).

Results

Participants with previous SARS-CoV-2 infection after a single vaccine dose elicited IgG (N) and IgG (S) antibody levels along with NAb binding inhibition responses levels were similar to infection-naïve vaccinated participants who had taken two doses of vaccine.

Interpretation & conclusions

Our preliminary data suggested that a single dose of BBV152-induced humoral immunity in previously infected individuals was equivalent to two doses of the vaccine in infection-naïve individuals. However, these findings need to be confirmed with large sized cohort studies.