Most viruses tend to constantly change structure due to mutations that produce new variants of the virus. Like other viruses, the COVID-19 virus or SARS-CoV-2 exists in several variants. The most common variants of concern for the COVID-19 virus are the alpha, beta, gamma, delta, and Omicron variants. In late 2020, the delta variant of the COVID-19 virus was identified in India and it has subsequently been detected in approximately 77 countries including the U.S. The delta variant is technically identified as SARS-CoV-2 B.1.617.2 and is characterized by mutations in its spike protein (S). Several of these mutations may affect immune responses and in turn, could cause a potentially higher rate of transmission than other variants.
For a period of time, the delta variant was responsible for most of the new COVID-19 cases in the U.S. The CDC identified the delta variant as a “variant of concern” and is monitoring the delta variant for transmission rates, ease of spread, severity of symptoms, and treatment responses.
A subvariant of the delta variant called the “delta plus” variant, has also been identified and appears to have a mutation that allows the virus to more effectively attack lung cells and potentially escape existing vaccines. The CDC as well as the World Health Organization have not labeled the "delta plus" subvariant as a variant of concern.
Currently, the dominant variant of the virus that causes COVID is the Omicron variant. The three most common lineages of the Omicron variant are the BA.2, BA.4, and BA.5. Research has shown that the Omicron variant spreads more easily than other variants.
The following is a summary of what we know about the delta variant:
- Currently, the Omicron variant is the most dominant variant of the virus causing COVID.
The delta variant of the COVID-19 virus is spreading with detection in at least 77 countries including the U.S. It has been classified as a “variant of concern” by the CDC and is being monitored for transmission rates, ease of spread, severity of symptoms, and treatment responses.
Infections with this variant have been discovered in some fully-vaccinated individuals. The appearance of the delta variant in fully-vaccinated people is termed “delta variant breakthrough infections.” Evidence suggests that fully-vaccinated individuals who become infected with the delta variant can spread the virus to others, however, vaccinated people appear to spread the virus for a shorter time. Lower amounts of viral genetic material were found in samples taken from fully-vaccinated people who had breakthrough infections than from unvaccinated people with COVID-19. It is thought that the viral genetic material may go down faster in fully vaccinated people when compared to unvaccinated people.
The present COVID-19 vaccines appear to provide protection against the delta variant. Although some fully-vaccinated individuals may become infected with the variant, it does appear at this time that the infection is likely less severe. Studies have shown that the two-dose vaccines have an effectiveness of 88% among persons with the delta variant. The vaccine effectiveness of one dose was notably lower among persons with the delta variant.
Given the evidence that the delta variant is circulating and spreading in the U.S, the latest CDC recommendation is for fully-vaccinated individuals to wear a mask in public indoor settings in areas of substantial or high transmission. Also, the recommendation is that fully-vaccinated people might choose to wear a mask regardless of the level of transmission, particularly if immunocompromised or at increase risk for severe disease. CDC also recommended that fully vaccinated individuals exposed to someone with COVID-19 be tested 3-5 days after exposure and wear a mask in public indoor settings for 14 days or until a negative test result. For teachers, staff, students, and visitors to schools, the CDC recommends universal indoor masking.
It appears that the vast majority of hospitalizations and deaths caused by COVID-19 are in unvaccinated people. Therefore, the greatest concern and risk of transmission of the delta variant is among unvaccinated people who are much more likely to become infected. At this time, the best way to protect against and reduce the spread of the delta variant is through COVID-19 vaccination.
The delta plus variant, a subvariant of the delta variant, has now been identified. This delta subvariant appears to have a mutation that allows the virus to more effectively attack lung cells and potentially escape existing vaccines. The CDC, as well as the World Health Organization, have not labeled this subvariant as a variant of concern. It is too early to determine the significance of this subvariant. More scientific studies are needed to determine the clinical implications of the delta plus variant.
