Ep 148-1: One of the early observations in April on replacement of the alpha (B.1.117) VOC by the delta (B.1.617.2) in Dehli. It is already noted that the delta VOC was prevalent in “vaccination breakthrough” cases. Not mentioned which vaccines, but presumably the Indian inactivated Covaxin and/or the Astra-Zeneca. Also not clear how many breakthroughs over total vaccinated subjects.
Ep 148-2: Rapid rise of delta variant in England between early April and late May.
Ep 148-3: The analysis of Riley et al. shows that delta rise is particularly important in children ang young people
We observed that growth was being driven by younger age groups, with five-fold higher rates of swab-positivity among younger children (ages 5 to 12 years) and young adults (18 to 24 years) compared with those aged 65 years and older….. These age patterns suggest that recent expansion of the vaccine programme to those aged 18 years and above  should help substantially to reduce the overall growth of the epidemic. The observed patterns may reflect increased social interactions among children and young adults as schools remain open and lockdown eases, as well as high vaccine uptake among older people.
Ep 148-4: Similar observation in Scotland: rapid rise during the period that vaccination was rolled out (April-June) and higher prevalence in younger people. Two doses of Pfizer protected 92 % against the RT-PCR confirmed infection with alpha and 79 % against delta. Corresponding figures for Astra-Zeneca were 73 % (alpha) and 60% (delta).
Risk of COVID-19 hospital admission was approximately doubled in those with the Delta VOC when compared to the Alpha VOC, with risk of admission particularly increased in those with five or more relevant comorbidities.
Ep 148-5: The analysis of vaccine efficacy by Bernal is restricted to symptomatic cases and more detailed:
- One dose of either Pfizer or AZ: 51% against alpha and 33 % again delta
- Two doses of Pfizer: 93 % alpha and 88 % delta
- Two doses of AZ: 66 % alpha and 60 % delta
- Not enough cases to estimate efficacy against severe disease or mortality
Ep 148-6: Alizon describes also a rapid rise of delta in the area of Paris. They conclude:
In absence of specic interventions and based on the current vaccine rollout, our model tailored to the French epidemic suggests that this could cause another epidemic wave starting in August 2021.
Ep 148-7: Similar observation in the US, noting that delta spreads especially rapidly in counties with low vaccination coverage.
Ep 148-8: A short note by the Center for Infectious Disease and Policy (U Minesote), indicating also spread in Israel and throughout Africa
Ep148-9: a nice paper in the Guardian, summarizing some of the papers above, with also an interesting quote of Public Health England:
… the Pfizer/BioNTech jab was linked to a 94% vaccine effectiveness against hospital admission with the Delta variant after one dose and 96% after two doses, while the figures for the Oxford/AstraZeneca jab were71% and 92% respectively.
My conclusion: Delta is on the rise and it is already starting the next wave all over the place, with a preference in younger and unvaccinated people. The good news is that vaccination can prevent the most serious consequences. So the take-home message: aim for the largest possible vaccination coverage, including the younger generations