The B.1.617.2 variant of the COVID-19 virus, first identified in India in December 2020 and designated as the Delta variant of concern (VOC) by the World Health Organisation, has changed the trajectory of the pandemic. Delta was the dominant variant fuelling India’s devastating second wave. In the United Kingdom, its prevalence rose from 1.7% of positive COVID-19 tests over a 5-week period in March-April to 99% of sequenced positive tests in July. It is also the dominant variant in the United States and is estimated to account for 70% of EU positive cases at the start of August, rising to 90% by the end of August.
Why Delta has been a game changer?
Several factors explain the growing dominance of the Delta variant. A large-scale China study found that viral loads were 1,260 times higher in those infected with the Delta variant compared with the historical strains 19A and 19B of the Wuhan variant of SARS-Cov2-2 on the day COVID-19 infection was detected. Another Chinese study found it takes a newly infected person with the Delta variant only 2.3 days on average to infect another person, compared to the 5.5-5.7 days it took for someone infected with the wildtype virus to infect another person early in the pandemic. Evidence of higher transmissibility was also found in the United Kingdom where Public Health England (PHE) data released in early June 2021 indicated the Delta variant at that point in time in England was associated with a 64% increased risk of household transmission compared with the Alpha (or UK) variant, including being 40% more transmissible outdoors. The symptoms commonly seen with Delta, which include runny nose and sore throat, have also differed from those reported with the earlier virus strains, leading many to assume they were experiencing a common cold and choose not to get tested or self-isolate. The higher transmissibility and reduced likelihood of infected individuals self-isolating have provided Delta with a competitive advantage compared to other COVID-19 variants, allowing it to become the dominant strain within several weeks after first entering a country.
In addition to being more transmissible, there are also early indications that Delta may be associated with more severe disease. A Scottish study published in The Lancet found that the risk of hospital admission was approximately doubled in individuals infected with the Delta variant compared to those with the Alpha variant. This was despite the Delta variant being found predominantly in younger and more affluent population groups. While it is uncertain if these results will be confirmed in further research, intensive care physicians have also been raising the alarm about high numbers of young people being hospitalized with COVID-19. In England about 20% of those hospitalized with COVID-19 in the week to 3 August were aged 18-34, compared to 5.5% during the winter surge. While the shift towards younger people is largely due to the success of vaccines, to which older age groups gained access earlier in the UK, doctors have warned that health risks to younger people remain significant. Meanwhile, in the US, Francis Collins, director of the National Institutes of Health (NIH), told ABC News on Sunday (8 August) that growing numbers of children are becoming ill with COVID-19 in the US, with 1,450 of them currently in hospital.
Implications for government policy
The higher transmissibility of the Delta variant is already triggering changes in government policy around the world and is expected to continue to do so in the future. A sharp rise in infection rates led to a delay in full reopening in the United Kingdom, for example.
Looking ahead, government policy in countries with sufficient vaccine supplies is likely to focus on encouraging vaccine uptake, potentially opening up vaccination to younger age groups, and offering a third vaccination to fully vaccinated individuals. While currently available vaccines work well against the Delta variant, it is clear that a second vaccination is required to achieve good immunity. A recent PHE study found that both Pfizer/BioNTech’s Comirnaty and AstraZeneca’s Vaxzevria were less effective against the Delta than against the Alpha variant after a single dose (estimated protective efficacy was 35.6% versus 47.5% for Comirnaty, and 30.0% versus 48.7% for Vaxzevria). However, the difference in effectiveness against the two variants was reduced after the second vaccination and was estimated at 93.7% (Alpha) versus 88% (Delta) for Comirnaty and 74.5% (Alpha) versus 67.0% (Delta) for Vaxzevria. Given this evidence, governments will undoubtedly seek to encourage as many people as possible to complete the full course of vaccinations and may delay full lifting of social distancing requirements until the second dose has been administered to vulnerable groups.
Governments are also more likely to pursue vaccination of younger age groups. University College London (UK) professor and advisor to the UK’s Independent Scientific Advisory Group for Emergencies (Independent SAGE), Karl Friston, recently concluded, as reported in The Guardian, that as of July, the R value in the UK was about 5, which suggests that instead of vaccinating 60-70% of the population, as was expected early in the pandemic, it may be necessary to vaccinate 80-85% in order to achieve vaccine-induced herd immunity against the Delta variant. Achieving such a high vaccination rate would only be possible if at least some children are also vaccinated. We are already seeing evidence of policy moving in this direction, with several European countries now joining the US to offer COVID-19 vaccination to under-16s and Israel offering vaccination to children aged 5 to 11 with serious medical conditions.
In addition, several countries including Israel, the UK, Uruguay, and Germany have now confirmed plans to re-inoculate groups of already vaccinated citizens with booster doses in an effort to provide additional protection as immunity starts to wane after the initial course of vaccination.
As countries with good access to vaccines embark on vaccinating ever-younger age groups and offering booster doses to fully vaccinated adults, securing access to vaccines in low- and middle-income countries will become even more difficult. The World Health Organization recently urged countries to ensure the most vulnerable population groups across the world are vaccinated first before offering vaccination to children. Whether these pleas are heeded remains to be seen.
One thing is certain: in all countries, the Delta variant has increased the risk of future lockdowns – presumably of a more limited nature than the initial ones – and that risk will rise if further virus mutations lead to variants as infectious as Delta, but with higher resistance to vaccines. Even if the risk of future lockdowns is averted, the pandemic will continue to affect healthcare spending and pharmaceutical sales as countries around the world attempt to clear the backlog of delayed medical services and endeavor to make their healthcare systems more resilient to future shocks. The immediate and long-term effects of such policies inform IHS Markit’s 10-year health expenditure and pharmaceutical sales forecasts.
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