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We assessed antibody responses 3 months post-vaccination in those who received mRNA-1273 (n=225), Sputnik V (n=128) or the first dose of Gam-COVID-Vac (n=184) and compared the results with previously reported data of Sinopharm and AZD1222 vaccinees. 99.5% of Moderna >94% of AZD1222 or Sputnik V, 72% to 76% of Gam-COVID-Vac (first dose) and 38.1% to 68.3% of Sinopharm vaccinees had ACE2 blocking antibodies above the positive threshold. The ACE2 blocking antibody levels were highest to lowest was Moderna > Sputnik V/ AZD1222 (had equal levels)> first dose of Gam-COVID-Vac > Sinopharm. All Moderna recipients had antibodies above the positive threshold to the ancestral (WT), B.1.1.7, B.1.351.1 and 80% positivity rate for B.1.617.2. Positivity rates of Sputnik V vaccinees for WT and variants, were higher than AZD1222 vaccinees, while Sinopharm vaccinees had the lowest positivity rates (<16.7%). These findings highlight the need for further studies to understand the effects on clinical outcomes.
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BackgroundTo understand the kinetics of immune responses with different dosing gaps of the AZD1222 vaccine, we compared antibody and T cell responses in two cohorts with two different dosing gaps. MethodsAntibodies to the SARS-CoV-2 virus were assessed in 297 individuals with a dosing gap of 12 weeks, sampled at 12 weeks post second dose (cohort 1) and in 77 individuals with a median dosing gap of 21.4 weeks (cohort 2) sampled 6 weeks post second dose. ACE2 receptor blocking antibodies (ACE2R-Abs), antibodies to the receptor binding domain (RBD) of the virus and variants of concern (VOC) and ex vivo T cell responses were assessed in a sub cohort. ResultsAll individuals (100%) had SARS-CoV-2 specific total antibodies and 94.2% of cohort 1 and 97.1% of cohort 2 had ACE2R-blocking Abs. There was no difference in antibody titres or positivity rates in different age groups in both cohorts. The ACE2R-blocking Abs (p<0.0001) and antibodies to the RBD of the VOCs were significantly higher in cohort 2, compared to cohort 1. 41.2% to 65.8% of different age groups gave a positive response by the haemagglutination assay to the RBD of the ancestral virus and VOCs in cohort 1, while 53.6% to 90% gave a positive response in cohort 2. 17/57 (29.8%) of cohort 1 and 17/29 (58.6%) of cohort 2 had ex vivo IFN{gamma} ELISpot responses above the positive threshold. The ACE2R-blocking antibodies and ex vivo IFN{gamma} ELISpot responses at 12 weeks post-first dose, significantly correlated with levels 12 weeks post second dose (Spearmans r=0.46, p=0.008) and (Spearmans r=0.71, p<0.0001) respectively. ConclusionsBoth dosing schedules resulted in high levels of antibody and T cell responses post vaccination, although those with a longer dosing gap had a higher magnitude of responses, possibly as immune responses were measured 6 weeks post second dose compared to 12 weeks post second dose.
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BackgroundAs there are limited data of the immunogenicity of the Sinopharm/BBIBP-CorV in different populations, antibody responses against different SARS-CoV-2 variants of concern and T cell responses, we investigated the immunogenicity of the vaccine, in individuals in Sri Lanka. MethodsSARS-CoV-2-specific antibodies were measured in 282 individuals who were seronegative at baseline, and ACE2 receptor blocking antibodies, antibodies to the receptor binding domain (RBD) of the wild type (WT), B.1.1.7, B.1.351 and B.1.617.2, ex vivo and cultured IFN{gamma} ELISpot assays, intracellular cytokine secretion assays and B cell ELISpot assays were carried out in a sub cohort of the vaccinees at 4 weeks and at 6 weeks (2 weeks after the second dose). Results95% of the vaccinees seroconverted, although the seroconversion rates were significantly lower (p<0.001) in individuals >60 years (93.3%) compared to those who were 20 to 39 years (98.9%). 81.25% had ACE2 receptor blocking antibodies at 6 weeks, and there was no difference in these antibody titres in vaccine sera compared to convalescent sera (p=0.44). Vaccinees had significantly less (p<0.0001) antibodies to the RBD of WT and B.1.1.7, although there was no difference in antibodies to the RBD of B.1.351 and B.1.617.2 compared to convalescent sera. 27.7% of 46.4% of vaccinees had ex vivo IFN{gamma} and cultured ELISpot responses respectively, and IFN{gamma} and CD107a responses were detected by flow cytometry. ConclusionsSinopharm/BBIBP-CorV appeared to induce high seroconversion rates and induce a similar level of antibody responses against ACE2 receptor, B.1.617.2 and B.1.351 as seen following natural infection.
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BackgroundWhile there have been many studies characterizing the IgG and IgA responses to different SARS-CoV-2 proteins in individuals with natural infection, the induction of IgG and IgA to different viral proteins in vaccinees have not been extensively studied. Therefore, we sought to investigate the antibody responses to SARS-CoV-2 following natural infection and following a single dose of AZD2221, in Sri Lankan individuals. MethodsUsing Luminex assays, we characterized the IgG and IgA responses in patients with varying severity of illness and following a single dose of the vaccine at 4 weeks and 12 weeks since onset of illness or following vaccination. Haemagglutination test (HAT) was used to assess the antibodies to the receptor binding domain of SARS-CoV-2 wild type (WT), B.1.1.7, B.1.351 and B.1.617.2 (VOCs) and surrogate neutralizing test to measure ACE2 receptor blocking antibodies. ResultsThose with mild illness and in vaccinees, the IgG responses to S1, S2, RBD and N protein increased from 4 weeks to 12 weeks, while it remained unchanged in those with moderate/severe illness. Those who had a febrile illness in 2017 and 2018 (controls) also gave IgG and IgA high responses to the S2 subunit. In the vaccinees, the most significant rise was seen for the IgG antibodies to the S2 subunit (p<0.0001). Vaccinees had several fold lower IgA antibodies to all the SARS-CoV-2 proteins tested than those with mild and moderate/severe illness at 4 weeks and 12 weeks. At 12 weeks the HAT titres were significantly lower to the B.1.1.7 in vaccinees and significantly lower in those with mild illness, and in vaccinees to B.1.351 and for B.1.617.2. No such difference was seen in those with moderate/severe illness. ConclusionsVaccinees had significantly less IgA to SARS-CoV-2, but comparable IgG responses to those with natural infection. However, following a single dose, vaccinees had reduced antibody levels to the variants of concern (VOC), which further declined with time, compared to natural infection.
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BackgroundAs the Municipality Council area in Colombo (CMC) experienced the highest number of cases until end of January 2021, in Sri Lanka, we carried out a serosurvey prior to initiation of the vaccination program to understand the extent of the SARS-CoV-2 outbreak. MethodsSARS-CoV-2 seropositivity was determined in 2547 individuals between the ages of 10 to 86 years, by the Wantai total antibody ELISA. We also compared to seroprevalence using the haemagglutination test (HAT) to evaluate its usefulness in carrying out serosurveys. ResultsThe overall seropositivity rate was 24.46%, while seropositivity by HAT was 18.9%. Although the SARS-CoV-2 infection detection rates by PCR were highest in the population between the ages of 20 to 60 years of age, the seropositivity rates were equal among all age groups. The seropositivity rate was highest in the 10 to 20 age group (34.03%), whereas the PCR positivity rates was 9.8%. Differences in the PCR positivity rates and seropositivity rates were also seen in 60- to 70-year-olds (8.9% vs 30.4%) and in individuals >70 year (4.1% vs 1.2%). The seropositivity rates of the females was 29.7% (290/976), which was significantly higher (p<0.002) than in males 21.2% (333/1571). ConclusionsA high seroprevalence rate (24.5%) was seen in all age groups in the CMC suggesting that a high level of transmission was seen during this area. The PCR positivity rates, appear to underestimate the true extent of the outbreak and the age groups which were infected.