Public Health England 20210611. SARS-CoV-2 variants of concern and variants under investigation in England Technical briefing 15. UK Government 2021, 11 June. https://www.theguardian.com/world/2021/jun/11/delta-variant-is-linked-to-90-of-covid-cases-in-uk
Among the first 33,206 people infected with the B.1.617.2 (‘Delta’) variant in England, 19,573 occurred in unvaccinated individuals, 1,785 among fully vaccinated people and 7,559 were among those who had received one dose or those with unclear vaccination status.
Pagel C. As England faces a third Covid wave, our most vulnerable may be losing protection. The Guardian 2021, published 7 June. Full text: https://www.theguardian.com/commentisfree/2021/jun/07/delta-variant-covid-england-vulnerable
“A new coronavirus variant that was first sequenced in India has been doubling about every eight days in England since early April. The Delta variant is now dominant in England, and according to a recent risk assessment from Public Health England (PHE), it has a substantially increased rate of transmissibility compared with the previously dominant variant Alpha, which was first sequenced in the UK. Having just a single dose of vaccination is less effective against Delta, and it may lead to a surge in hospital cases.”
Wall EC, Wu M, Harvey G, et al. Neutralising antibody activity against SARS-CoV-2 VOCs B.1.617.2 and B.1.351 by BNT162b2 vaccination. Lancet 2021, published 3 June. Full text: https://doi.org/10.1016/S0140-6736(21)01290-3
Antibody levels of individuals vaccinated with the Pfizer vaccine are on average lower against B.1.617.2 (the SARS-CoV-2 variant first identified in India, named ‘Delta’ by WHO). The authors show that neutralizing antibody titers were 5.8-fold reduced against B.1.617.2 relative to the historical Wuhan strain, significantly more reduced than against B.1.1.7 (2.6-fold), and comparable to the reduction observed against B.1.351 (4.9-fold). Both increased age and time since the second dose of the Pfizer vaccine correlated with decreased activity against B.1.617.2 and B.1.351.
Recently, the cumulative 7-day incidence has been rising in the UK (see Our World in Data), probably fueled by transmission of B.1.617.2. Organizing the Champions League final in the Portuguese city of Porto may not have been a good idea.
Public Health England 20210603. SARS-CoV-2 variants of concern and variants under investigation in England Technical briefing 14. UK Government 2021, updated 3 June – accessed 4 June 2021. https://www.gov.uk/government/publications/investigation-of-novel-sars-cov-2-variant-variant-of-concern-20201201
Public Health England reports that
- B.1.617.2 (the ‘Delta’ variant) shows a substantially increased growth rate compared to B.1.1.7 (‘Alpha’)
- Secondary attack rates remain higher for B.1.617.2 among both household and non-household contacts
- Early data from both England and Scotland suggest an increased risk of hospitalisation with B.1.617.2 compared to B.1.1.7
Salo J, Hagg M, Kortelainen M, et al. The indirect effect of mRNA-based Covid-19 vaccination on unvaccinated household members. medRxiv 2021, posted 29 May. Full text: https://doi.org/10.1101/2021.05.27.21257896
The mRNA-based vaccines (BioNTech/Pfizer and Moderna) might lead to a substantial reduction in infections among unvaccinated household members (Salo 2021). The authors estimate an effectiveness of 8.7% two weeks after the first dose and 42.9% after 10 weeks.