By Dora Anne Mills, MD, MPH, Chief Health Improvement Officer at MaineHealth

Delta’s dawn

An article in Sunday’s Portland Press Herald/Sunday Telegram by Colin Woodard reviews new data about the entrance of COVID-19’s delta variant into Maine.

We’ve been very fortunate to have MaineHealth’s NorDx Lab using a new screening test for variants. Since 7/1, out of the 49 tests that have been run, 18 screened positive for the delta variant (B.1.617.2, “Indian”), 4 for alpha (B.1.1.7, “U.K.”), and 2 for gamma (P.1, “Brazilian”). This screening is done for epidemiological purposes (and not for clinical purposes), including since there are currently no clinical treatment differences based on variants. These screening test results are preliminary and are pending validation by genetic sequencing through the Maine CDC (which is conducted by JAX in Connecticut or sometimes US CDC). Genetic sequencing is a very complicated and time-consuming process, hence the development of some variant screening tests, which so far, indicate the delta variant is in Maine. However, Delta’s appearance is completely expected.

A few points about delta


It appears the delta variant may cause common cold symptoms such as a headache, sore throat, and runny nose, as well as a fever and cough, but reportedly often does not cause the typical loss of taste and smell. Therefore, if someone thinks they only have a summer cold, they should probably be tested for COVID-19.


Delta is much more contagious than the Alpha variant. It is estimated to be about 225% more contagious than the original strains and has the capacity to be the first one to achieve dominance globally.

A study from China published July 7th indicates the delta variant grows more rapidly and to higher levels, as measured by viral loads with delta being 1,000 times higher than those infected with the original strain, and with virus becoming detectable four days after exposure, rather than six. These findings may help explain why delta Is much more transmissible.


Delta may be more virulent. It’s not entirely clear if it is more virulent or if the increase in transmissibility is resulting in more people being infected and therefore more people being hospitalized. However, two studies from the U.K. and one from Canada shed some concerning light:

  • A Scottish study published June 14th indicates those who are unvaccinated with delta are twice as likely to be hospitalized than those sick with the Alpha variant.
  • Data from England published June 11th on 38,805 cases found that after controlling for age, sex, ethnicity, and vaccination status, people infected with the delta variant had a 2.61 greater risk of being hospitalized within 14 days of infection compared with those infected with the alpha variant.
  • A study from Canada published July 5th indicates significant increased risk of hospitalization, ICU admission, and death with the delta variant over the alpha variant and previous strains.

Vaccine Efficacy

The current three vaccines authorized in the U.S. appear to provide strong protection against death and hospitalization from the delta variant. However, they appear to offer less robust protection against minor to moderate infection.

For instance:

  • Public Health England data published July 8th indicate that while their current vaccines (Pfizer and Astra Zeneca) are effective against hospitalizations from delta (80% after a first dose; 96% after second dose), they may not be as effective against symptomatic disease (35% after a first dose; 79% after second dose).
  • Findings from Canada published July 3rd are similar, indicating lower protection from a single dose of vaccine (Pfizer, Moderna), but excellent protection against severe disease after both doses.
  • Israel announced on July 6th that the Pfizer vaccine (the only vaccine Israel is administering) is 64% effective against infection and symptomatic illness, down from 95% in May, and is 93% effective against severe disease and hospitalization. This analysis is based on the concurrent rise in the delta variant to now accounting for >95% of all samples that are sequenced in Israel.
  • In a very small lab-based study, pre-published by J&J on July 1, blood from eight vaccinated individuals exposed to the delta variant produced a robust immune response, including neutralizing antibodies.

The bottom line Is that so far, the data Indicate the vaccines authorized in the U.S. and Europe are providing very excellent protection from severe disease. However, they may not be as protective against mild or asymptomatic infections.This Is one reason why if you’re fully vaccinated and in close contact (sharing breathed air) with people you’re unsure of their vaccine status or who are unvaccinated, you may want to consider masking and distancing, especially If they are unmasked or if you’re immune-compromised or if you’re an older person with chronic conditions.



Much of Maine’s disparities in vaccine rates are rural. Across different age groups eligible for vaccine, those living in rural counties and zip codes have lower rates than urban ones. Among younger age groups of teens and young adults, some rural county rates are half that of Cumberland County (Maine’s most urban county).


Maine has seen few racial and ethnic disparities in its vaccination rates. A higher percentage of Black and Asian people in age groups eligible for vaccine are vaccinated in Maine compared to White people. The same is true for Hispanic people compared with non-Hispanic people. Although there are limited data available for Maine’s Tribal members because much of the vaccine is distributed directly to the Tribes through federal sources, the available data indicate there may be similar trends for people 50 and older who identify as Native American.


Although COVID disease activity (as measured by incidence and test positivity rates) is decreasing in most places in Maine, rural counties have the highest rates of both. In general, rural counties in New England and many other parts of the country have higher incidence and test positivity rates than more rural counties.


We’re finding some cases of COVID among those who are fully vaccinated. So far, the very vast majority have been either asymptomatic or with mild infection, or are immune-compromised or elderly with significant co-morbid conditions. As our vaccine rates increase, it is likely we will see more with COVID who are fully vaccinated. That does not mean the vaccine has lost Its effectiveness. The statistical explanation is basically a matter of denominators. When say 85% of the population is vaccinated and 5% of them contract COVID (assuming vaccine is 95% effective), that is a higher number than if 20% of the 15% of the population who are unvaccinated contracts COVID. In the sources below is a link to a great illustration of this. The good news is even as cases rise among those who are fully vaccinated, they’re still very protected and highly unlikely to become seriously ill.

As the delta variant spreads around the globe like an invasive plant, choking other variants and finding the unvaccinated as fertile ground, we in Maine and New England are most fortunate to live in one of the safest places on the planet. We have built a formidable wall to protect us against the pandemic and that’s the wall of high vaccine rates. We also are fortunate to have easy access to the tools of distancing, masking, ventilation, and testing. In order to choke delta and future variant Invasive species, we need to assure all have access to vaccine — here as well as everywhere in the world. Delta’s dawning In Maine and elsewhere in the U.S. is a reminder that we are far from closing the books on this pandemic.

Additional sources: