Introduction The Delta variant of SARS-CoV-2 has caused a new wave of the COVID-19 epidemic in many countries. It is the most infectious variant of SARS-CoV-2 to date, and its high infectivity means that a higher proportion of the population needs to be vaccinated to reduce the disease burden, which poses a substantial public health challenge. Areas covered The evolution of the Delta variant is reviewed, including an overview of the Delta Plus variant with a K417N mutation in the RBD, which may confer an improved immune evasion ability. Decreases in serum neutralizing antibody titers after vaccination against Delta were greater than those against Alpha but less than those against Beta. The protective efficacy of existing vaccines against the Delta variant have declined and is related to the number of doses and the time since vaccination. Expert opinion The currently used vaccines are effective against hospitalization/severe disease due to the Delta variant. Accelerating the popularization of vaccination, improving the coverage rate, and the implementation of intervention measures, such as wearing masks, are effective means to control the spread of the Delta variant and other variants. However, vaccination alone against SARS-CoV-2 without intervention measures may lead to continuous spread and the emergence of new variants.

https://www.tandfonline.com/doi/pdf/10.1080/14760584.2021.1976153

Impact of the Delta variant on vaccine efficacy and response strategies.

Accelerated COVID-19 vaccine development: milestones, lessons, and prospects.

Since the outbreak of coronavirus disease 2019 (Covid-19) in December 2019, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the number of confirmed infections has risen to more than 242 million worldwide, with nearly 5 million deaths. Currently, nine Covid-19 vaccine candidates based on the original Wuhan-Hu-1 strain are at the forefront of vaccine research. All nine had an efficacy over 50% against symptomatic Covid-19 disease: NVX-CoV2373 (∼96%), BNT162b2 (∼95%), mRNA-1273 (∼94%), Sputnik V (∼92%), AZD1222 (∼81%), BBIBP-CorV (∼79%), Covaxin (∼78%), Ad26.CoV.S (∼66%) and CoronaVac (∼51%). However, vaccine efficacy (VE) can be jeopardised by the rapid emergence and spread of SARS-CoV-2 variants of concern (VOCs) that could escape from neutralising antibodies and/or cell-mediated immunity. Rare adverse events have also been reported soon after administration of viral vector and mRNA vaccines. Although many Covid-19 vaccines have been developed, additional effective vaccines are still needed to meet the global demand. Promising Covid-19 vaccines such as WIBP-CorV, AD5-nCOV, ZyCoV-D, CVnCoV, EpiVacCorona and ZF2001 have advanced to clinical studies. This review describes the most relevant mutations in the SARS-CoV-2 spike protein, discusses VE against VOCs, presents rare adverse events after Covid-19 vaccination and introduces some promising Covid-19 vaccine candidates.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/rmv.2313

Covid-19 vaccines and variants of concern: A review.

In April 2021, after successfully enduring three waves of the SARS-CoV2 pandemic in 2020, and having reached population seropositivity of about 50%, Delhi, the national capital of India was overwhelmed by the fourth wave Here, we trace viral, host, and social factors contributing to the scale and exponent of the fourth wave, when compared to preceding waves, in an epidemiological context Genomic surveillance data from Delhi and surrounding states shows an early phase of the upsurge driven by the entry of the more transmissible B117 variant of concern (VOC) into the region in January, with at least one B117 super spreader event in February 2021, relatable to known mass gatherings over this period This was followed by seeding of the B1617 VOC, which too is highly transmissible, with rapid expansion of B16172 sub-lineage outpacing all other lineages This unprecedented growth of cases occurred in the background of high seropositivity, but with low median neutralizing antibody levels, in a serially sampled cohort Vaccination breakthrough cases over this period were noted, disproportionately related to VOC in sequenced cases, but usually mild We find that this surge of SARS-CoV2 infections in Delhi is best explained by the introduction of a new highly transmissible VOC, B16172, with likely immune-evasion properties; insufficient neutralizing immunity, despite high seropositivity; and social behavior that promoted transmission

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Genomic characterization and Epidemiology of an emerging SARS-CoV-2 variant in Delhi, India

Key Points Question What are the rate of reinfection of SARS-CoV-2 among a cohort of health care workers (HCWs) and the estimated effectiveness of the inactivated whole virion vaccine BBV152 against reinfection? Findings In this cohort study of 4978 HCWs who were infected with SARS-CoV-2 from March 3, 2020, to June 18, 2021, the incidence density of reinfection was 7.26 per 100 person-years. A protective association of 86% against reinfection was observed among HCWs who completed the 2-dose schedule of BBV152 and for whom at least 15 days elapsed without reinfection after vaccination. Meaning The results of this study suggest that complete vaccination with BBV152 among HCWs in India is crucial, including in persons previously infected with SARS-CoV-2.

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SARS-CoV-2 Reinfection Rate and Estimated Effectiveness of the Inactivated Whole Virion Vaccine BBV152 Against Reinfection Among Health Care Workers in New Delhi, India

BackgroundWe report the clinical efficacy against COVID-19 infection of BBV152, a whole-virion inactivated SARS-CoV-2 vaccine formulated with a Toll-like receptor 7/8 agonist molecule adsorbed to alum (Algel-IMDG). MethodsWe did a double-blind, randomised, multicentre, phase 3 clinical trial in 25 Indian hospitals to evaluate the efficacy, safety, and immunological lot consistency of BBV152. Healthy adults (age 18-98 years) randomised 1:1 using a computer-generated randomisation scheme received two intramuscular doses of vaccine or placebo administered four weeks apart. The primary outcome was laboratory-confirmed symptomatic COVID-19, occurring at least 14 days after the second dose. Secondary outcomes were efficacy in sub-groups for age (18-< 60 years and [≥] 60 years) and in participants with pre-existing stable medical conditions. We also evaluated safety, reactogenicity, and consistency of immune responses for three consecutive manufacturing lots. FindingsBetween November 16, 2020 and January 7, 2021 we recruited 25,798 participants who were randomised to BBV152 or placebo groups; 24,419 received two doses of BBV152 (n = 12,221) or placebo (n = 12,198). In a case-driven analysis, 130 cases of symptomatic COVID-19 were reported in 16,973 (0{middle dot}77%) participants with follow-up at least two weeks after the second vaccination; 24 occurred in the vaccine group and 106 in placebo recipients giving an overall vaccine efficacy of 77{middle dot}8% (95% CI: 65{middle dot}2-86{middle dot}4). Sixteen cases, one vaccinee and 15 placebo recipients, met the severe symptomatic COVID-19 case definition giving a vaccine efficacy of 93{middle dot}4% (57{middle dot}1-99{middle dot}8). Efficacy against asymptomatic COVID-19 was 63{middle dot}6% (29{middle dot}0-82{middle dot}4). BBV152 conferred 65{middle dot}2% (95% CI: 33{middle dot}1-83{middle dot}0) protection against the SARS-CoV-2 Variant of Concern, B.1.617.2 (Delta). BBV152 was well tolerated with no clinically or statistically significant differences in the distributions of solicited, unsolicited, or serious adverse events between vaccine and placebo groups. No cases of anaphylaxis or vaccine-related deaths were reported. InterpretationBBV152 was immunogenic and highly efficacious against symptomatic and asymptomatic COVID-19 variant associated disease, particularly against severe disease in adults. Vaccination was well tolerated with an overall incidence of adverse events observed over a median of 146 days that was lower than that observed with other COVID-19 vaccines. FundingThis work was supported and funded by Bharat Biotech International Limited and partly co-funded by the Indian Council of Medical Research. Clinicaltrials.gov: NCT04641481

https://www.medrxiv.org/content/medrxiv/early/2021/07/02/2021.06.30.21259439.full.pdf

Raches Ella Mbbs

Papers

Efficacy, safety, and lot to lot immunogenicity of an inactivated SARS-CoV-2 vaccine (BBV152): a double-blind, randomised, controlled phase 3 trial