The arrival of the Delta variant has opened another chapter in the COVID-19 pandemic. Delta emerged in India this spring and was responsible for the devastating surge in April through June that caused more than 15 million infections and 200,000 deaths — according to the official numbers, which all experts agree are grossly understated.
Since then, Delta has spread to Britain and Europe, and is catalyzing surges in Africa. Delta is the dominant strain within the United States; Los Angeles is now recommending that everyone wear masks indoors regardless of their vaccination status in response to the rise in Delta variant cases.
What does this mean for Massachusetts? With over 70 percent of residents vaccinated, Bay State residents are generally well protected against this variant. However, those who still have not received their vaccination or who have missed their second dose urgently need to get theirs.
Because of Delta’s increased transmissibility, those who are unvaccinated have as high a risk of COVID infection as in the late January surge and cannot rely on the herd immunity of the surrounding population. Delta is the most worrisome so far of all the variants, and the unvaccinated or partially vaccinated of all ages are most at risk.
Delta is nasty. The variant is 60 percent more transmissible than the Alpha variant (also known as the UK strain), and double that of the original strain. Recent data suggest that Delta is also more dangerous and could double the risk of hospitalization.
Delta is fueling a rise in infection rates across the nation after steady declines in the spring, and those rates are expected to grow as travel continues to pick up and social distancing and masking decline.
Thankfully, vaccines in use in the US appear to be highly effective against the Delta strain. Johnson & Johnson reported only a small reduction in efficacy against the variant. The Pfizer vaccine has been shown to be 88 percent effective against Delta and serious illness, although smaller studies in Israel show protection against infection and symptomatic illness drops to 64 percent. One dose provides only 34 percent protection against Delta; if you are one of the 475,000 Massachusetts residents who has not yet received their second shot, be sure to do so. Moderna’s mRNA vaccine is expected to be similarly protective. As more studies are completed, we will get a clearer picture of how well vaccines work against Delta. So far the signs are generally positive.
No vaccine is perfect, and while breakthrough infections are exceedingly rare, they still do happen. It is wise to continue to mask up while in crowded indoor spaces, and absolutely critical if traveling to states like Florida or Arizona where less than 50 percent of people are vaccinated.
With the emergence of Delta coming even after months of painful lockdowns and on the heels of a positive US vaccine rollout, it is understandable to feel like COVID will never end.
However, there are grounds for hope. Delta can be contained if we keep driving toward 80-90 percent vaccine coverage by reaching young people and children age 12 to 16 who became eligible in April. If the current vaccines are approved for people age 2 to 12 in the fall as currently expected, that will also boost population level immunity. For everyone, vaccinated and unvaccinated, wearing masks in crowds will also be a positive contribution to reducing the spread of existing variants, notwithstanding the current Centers for Disease Control and Prevention guidance.
There are also biological grounds for optimism — there is the possibility that with Delta, SARS-CoV2 has reached “peak fitness,” where the virus has mutated to become maximally transmissible. While it’s too soon to tell, Delta could be the “final variant” that remains dominant, with only minor additional mutations possible.
But it is also possible that there will be more variants with greater transmissibility and severity of disease, and as long as COVID continues to circulate among the unvaccinated there are greater chances of more variants emerging.
After the general feeling of helplessness last year, COVID-19 — including the Delta variant — is totally preventable in 2021. In the eight months since their launch, available vaccines have been proven to be safe and highly effective; they are free and now abundantly accessible to US residents. Every new case, whether mild or severe, is unnecessary.
Run, do not walk, to get your shot, if you haven’t been vaccinated already. Together we can blunt Delta and any of its cousin variants that might be out there waiting to burst on the scene.
Shan Soe-Lin is managing director of Boston-based Pharos Global Health Advisors and a lecturer in global health at the Jackson Institute for Global Affairs at Yale University. Robert Hecht is the president of Pharos Global Health Advisors and a clinical professor of epidemiology at the Yale School of Public Health.