Delta means change. Unfortunately, the change is disastrous as far as covid virus lineage goes. Delta variant, also known as B.1.617.2, is the name of the virus causing the present wave in India christened by the WHO. The Delta variant has been linked to a resurgence of COVID-19 in multiple countries. The Delta variant is threatening a third wave in the United Kingdom. It has already spread to forty-one states in the United States of America.
Delta is moderately resistant to vaccines, particularly in people who have received just a single dose. However, a recently published study found that a single dose of either AstraZeneca's or Pfizer's vaccine reduced a person's risk of developing COVID-19 symptoms caused by the Delta variant by 33%, compared to 50% for the Alpha variant. A second dose of the AstraZeneca vaccine boosted protection against Delta to 60% (compared to 66% against Alpha). In comparison, two doses of Pfizer's vaccines were 88% effective (compared to 93% against Alpha). Based on this Govt of UK public health release, The difference in effectiveness between the vaccines after 2 doses may be explained by the fact that rollout of second doses of AstraZeneca was later than for the Pfizer-BioNTech vaccine. Studies of antibody profiles post-vaccination also show it takes longer to reach maximum effectiveness with the AstraZeneca vaccine. However, a recent release from the same source confirmed that the Pfizer-BioNTech vaccine is 96% effective against hospitalization after 2 doses. In comparison, the Oxford-AstraZeneca vaccine is 92% effective against hospitalization after 2 doses. Thus they have similar efficacy.
All vaccines are unfortunately not the same. Clinical trials in Brazil with the Chinese vaccine developed by Sinovac called CoronaVac estimated that vaccine effectiveness of 49.6% following at least one dose and was 50.7% two weeks after the second dose. A recent news report by a respected news agency claimed that over 350 doctors and medical staff in Indonesia developed COVID-19 despite receiving CoronaVac.
The Delta variant is way more transmissible than the alpha variant and is also much deadlier. Experience shows that it is twice as likely to get infected individuals to end up in a hospital. However, rapid vaccination is the answer to both containing this variant or any other variant that might arise due to progressive mutation of the virus as infections continue to simmer worldwide with lack of vaccination. A rapid vaccination campaign with public education of its importance is the mantra to contain this wave and possibly avoid or attenuate a third.
(The author is a cardiologist and professor. He is based in Memphis, TN, USA. Views expressed are personal and do not necessarily reflect those of Outlook Magazine.)