Several COVID-19 vaccines have received emergency approval. Here we assess the immunogenicity of a single dose of the AZD1222 vaccine, at one month, in a cohort of health care workers (HCWs) (629 naïve and 26 previously infected). 93.4% of naïve HCWs seroconverted, irrespective of age and gender. Haemagglutination test for antibodies to the receptor binding domain (RBD), surrogate neutralization assay (sVNT) and ex vivo IFNγ ELISpot assays were carried out in a sub-cohort. ACE2 blocking antibodies (measured by sVNT) were detected in 67/69 (97.1%) of naïve HCWs. Antibody levels to the RBD of the wild-type virus were higher than to RBD of B.1.1.7, and titres to B.1.351 were very low. Ex vivo T cell responses were observed in 30.8% to 61.7% in naïve HCWs. Previously infected HCWs, developed significantly higher (p < 0.0001) ACE2 blocking antibodies and antibodies to the RBD for the variants B.1.1.7 and B.1.351. This study shows high seroconversion after one vaccine dose, but also suggests that one vaccine dose may be insufficient to protect against emerging variants.

Background To determine the kinetics and persistence of immune responses following the Sinopharm/BBIBP‐CorV, we investigated immune responses in a cohort of Sri Lankan individuals. Methods SARS‐CoV‐2 specific total antibodies were measured in 20–39 years ( n = 61), 40–59 years ( n = 120) and those >60 years of age ( n = 22) by enzyme‐linked immunosorbent assay, 12 weeks after the second dose of the vaccine. Angiotensin‐converting enzyme 2 (ACE2) receptor blocking antibodies (ACE2R‐Ab), antibodies to the receptor‐binding domain (RBD) of the ancestral virus (WT) and variants of concern, were measured in a sub cohort. T cell responses and memory B cell responses were assessed by ELISpot assays. Results A total of 193/203 (95.07%) of individuals had detectable SARS‐CoV‐2 specific total antibodies, while 67/110 (60.9%) had ACE2R‐Ab. A total of 14.3%–16.7% individuals in the 20–39 age groups had detectable antibodies to the RBD of the WT and variants of concern, while the positivity rates of those ≥60 years of age was <10%. A total of 14/49 (28.6%) had Interferon gamma ELISpot responses to overlapping peptides of the spike protein, while memory B cell responses were detected in 9/20 to the S1 recombinant protein. The total antibody levels and ACE2R‐Ab declined from 2 to 12 weeks from the second dose, while ex vivo T cell responses remained unchanged. The decline in ACE2R‐Ab levels was significant among the 40–59 ( p = .0007) and ≥60 ( p = .005) age groups. Conclusions Antibody responses declined in all age groups, especially in those ≥60 years, while T cell responses persisted. The effect of waning of immunity on hospitalization and severe disease should be assessed by long term efficacy studies.

Severe pneumonia and multiorgan dysfunction in COVID-19 and dengue haemorrhagic fever (DHF) are two diseases that can associate with an altered immune response to the infecting virus. To determine the similarities and differences in the cytokine and chemokine responses in these two infections, we compared responses in patients with varying severity of COVID-19 and acute dengue at different time points of illness. During early disease, patients who proceeded to develop COVID-19 severe pneumonia (SP) and DHF had significantly higher levels of IL-6, IL-10 and MIP3α than those who developed mild illness. The lowest levels of IFNγ in early illness were seen in those who succumbed to their illness due to COVID-19. Levels of serum IL-10 (p = 0.0001), IL-6 (p = 0.002), MIP-3α (p = 0.02) and CD40-L levels (p = 0.002) significantly increased from 5 to 9 day of illness to 10–21 day of illness in patients with moderate-to-severe COVID-19, but not in those with mild illness. In contrast, these cytokine/chemokine levels remained unchanged in those with DHF or dengue fever (DF) during febrile and critical phases. Although IL-10 levels were significantly higher in COVID-19 patients with SP, patients with DHF had 25-fold higher levels, whereas IL-6 levels were 11-fold higher in those with COVID-19 SP. IL-10 and other cytokines were evaluated in a larger cohort of patients during early illness (≤ 4 days) who proceeded to develop DF (n = 71) or DHF (n = 64). Of the cytokines evaluated, IL-10 was significantly higher (p < 0.0001) in those who went on to develop DHF compared to DF. Low IFNγ response to the SARS-CoV2 and high levels of immunosuppressive IL-10 in both COVID-19 and dengue during early illness are indicators of an altered antiviral response potentially contributing to disease severity.

Abstract Severe pneumonia and multiorgan dysfunction in COVID-19 and dengue haemorrhagic fever (DHF) are two diseases that can associate with an altered immune response to the infecting virus. To determine the similarities and differences in the cytokine and chemokine responses in these two infections, we compared responses in patients with varying severity of COVID-19 and acute dengue at different time points of illness.During early disease, patients who proceeded to develop COVID-19 severe pneumonia (SP) and DHF had significantly higher levels of IL-6, IL-10 and MIP3α than those who developed mild illness. The lowest levels of IFNγ in early illness were seen in those who succumbed to their illness due to COVID-19. Levels of serum IL-10 (p=0.0001), IL-6 (p=0.002), MIP-3α (p=0.02) and CD40-L levels (p=0.002) significantly increased from 5-9 day of illness to 10-21 day of illness in patients with moderate-to-severe COVID-19, but not in those with mild illness. In contrast, these cytokine/chemokine levels remained unchanged in those with DHF or dengue fever (DF) during febrile and critical phases. Although IL-10 levels were significantly higher in COVID-19 patients with SP, patients with DHF had 25-fold higher levels, whereas IL-6 levels were 11-fold higher in those with COVID-19 SP. IL-10 and other cytokines were evaluated in a larger cohort of patients during early illness (≤ 4 days) who proceeded to develop DF (n=71) or DHF (n=64). Of the cytokines evaluated, IL-10 was significantly higher (p<0.0001) in those who went on to develop DHF compared to DF. Low IFNγ response to the SARS-CoV2 and high levels of immunosuppressive IL-10 in both COVID-19 and dengue during early illness are indicators of an altered antiviral response potentially contributing to disease severity.

Due to limited access to vaccines, many countries have only administered a single dose of the AZD1222, whereas the dosage intervals have increased ≥4 wk. We sought to investigate the immunogenicity of a single dose of vaccine at ≥16 wk postimmunization. Severe acute respiratory syndrome coronavirus 2–specific Abs in 553 individuals and Abs to the receptor-binding domain of the Wuhan virus (wild-type) and the variants of concern, angiotensin-converting enzyme 2 receptor blocking Abs ex vivo and cultured IFN-γ T cell (Homo sapiens) responses and B cell (H. sapiens) ELISPOT responses, were investigated in a subcohort. The seropositivity rates in those &gt;70 y of age (93.7%) was not significantly different compared with other age groups (97.7–98.2; Pearson χ2 = 7.8; p = 0.05). The Ab titers (Ab index) significantly declined (p &lt; 0.0001) with increase in age. A total of 18 of 69 (26.1%) of individuals did not have angiotensin-converting enzyme 2 receptor–blocking Abs, whereas responses to the receptor-binding domain of wild-type (p = 0.03), B.1.1.7 (p = 0.04), and B.1.617.2 (p = 0.02) were significantly lower in those who were &gt;60 y. Ex vivo IFN-γ T cell ELISPOT responses were seen in 10 of 66 (15.1%), whereas only a few expressed CD107a. However, &gt;85% had a high frequency of cultured IFN-γ T cell ELISPOT responses and B cell ELISPOTs. Virus-specific Abs were maintained at ≥16 wk after receiving a single dose of AZD1222, although levels were lower to variants of concern, especially in older individuals. A single dose induced a high frequency of memory T and B cell responses.