Human vaccines & immunotherapeutics news: July 2020.

Abstract

The Delta variant of SARS-CoV-2 is rapidly spreading worldwide. The hyper-transmissible strain has been shown to achieve >1,000-fold higher viral load in infected people than the parent Alpha strain, with symptom onset an average of 2 days earlier. Nonetheless, vaccination does work against the disease: a study from England indicates that two doses of the BNT162b2 vaccine (Pfizer & BioNTech) prevent 88% and 94% of symptomatic disease caused by the Delta and Alpha variants, respectively. Protection was 67% and 75%, respectively, for the ChAdOx1 nCoV-19 vaccine (AstraZeneca). Vaccination also prevents transmission, according to three studies conducted before the onset of the Delta strain. The BNT162b2 vaccine prevented 80% of infections, and although the decrease in transmission rate in vaccinated people varied from 40% to 80% in these studies, the combined effect resulted in >88% lower risk of SARS-CoV-2 transmission within households. The mRNA-1273 vaccine (Moderna) elicits durable cellular and humoral immunity, which is comparable to that in convalescent individuals, even if just a quarter of the regular dose is administered. The scientists, who followed 35 participants of the original dose-escalation trial 7 months after vaccine administration, hope that lower doses might ease the global shortage in vaccine supplies. Covid-19 might also be treated via passive immunization. The antibody S2H97, which is based on a panel of antibodies isolated from people recovering from SARS-CoV-2 or SARS-CoV infection, can bind to multiple strains of SARS-CoV-2 and other related coronaviruses and prevent infection in cell culture and a hamster model. The whole-virion inactivated vaccine candidate Covaxin (Ocugen) demonstrated 78% efficacy against Covid-19 (93% against severe disease) in a Phase 3 trial involving 26,000 adults. Covaxin offered better protection against the Delta strain than previous infection with the parent virus. In contrast, another mRNA vaccine CVnCoV (CureVac) failed in a late-stage clinical trial involving 40,000 people. The vaccine showed 47% efficacy following two doses.