Episode 65: Delta Variant.
Harendra and Dr Arreaza present current evidence regarding the delta variant of SARS-CoV-2 (COVID-19), effectiveness of vaccines, and more.
Introduction: Booster shots for the COVID-19 vaccine.
The Department of Health and Human Services (HHS) announced in a statement dated August 18, 2021, that “a booster shot will be needed to maximize vaccine-induced protection and prolong its durability.”
This fall people may start getting their booster shots of mRNA vaccines (i.e. Pfizer and Moderna) as long as 8 months have passed since their second dose of the vaccine. The estimated date to start giving booster shots is the week of September 20, 2021.
It is anticipated that patients who received the J&J vaccine will also need a booster shot, but more data is needed to make it official. So, stay tuned for updates.
This is Rio Bravo qWeek, your weekly dose of knowledge brought to you by the Rio Bravo Family Medicine Residency Program from Bakersfield, California. Our program is affiliated with UCLA, and it’s sponsored by Clinica Sierra Vista, Let Us Be Your Healthcare Home.
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Delta Variant – The Science
By Harendra Ipalawatte, MS4, and Hector Arreaza, MD.
A growing concern and much of the recent talk about COVID 19 has been revolving around the emerging delta variant as well as other noted virus around the world different from the alpha strain. Much like the influenza virus and swine flu, SARS-CoV-2 seems to be changing and adapting in its current form.
On July 27, 2021, the CDC recommended to urgently increase COVID-19 vaccination and reinforced the need to wear a mask in public indoor places in areas of high risk for transmission, even for fully vaccinated people.
Concerns about Delta
CDC issued this new guidance due to several concerning developments and newly emerging data signals.
There is a reversal in the downward trajectory of cases. CDC has seen a rapid and alarming rise in the COVID case and hospitalization rates around the country. In late June 2021, the 7-day moving average of reported cases was around 12,000. In contrast, on July 27, the 7-day moving average of cases reached over 60,000. This case rate looked more like the rate of cases we had seen before the vaccine was widely available.
New data shows the delta variant is more infectious even in vaccinated individuals. Data was taken from CDC and unpublished surveillance data that will be posted soon. Delta causes more infections and spreads faster than early forms of SARS-CoV-2. Delta has shown to be more than 2x as contagious as previous variants.
The delta variant might cause more severe illness than previous strains in unvaccinated persons. In two different studies from Canada and Scotland, patients infected with the delta variant were more likely to be hospitalized than patients infected with alpha or the original virus strains.
Delta is currently the predominant strain of the virus in the United States.
Unvaccinated people are considered the greatest concern
Breakthrough infections (i.e., infections in patients who are fully vaccinated) happen less often than infections in unvaccinated people, all symptomatic patients infected with the delta variant can transmit it to others.
CDC is studying the data on whether fully vaccinated people with asymptomatic breakthrough infections can transmit the infection. However, the greatest risk of transmission is among unvaccinated people who are much more likely to contract and transmit the virus.
Fully vaccinated people with delta breakthrough infections can spread the virus to others. However, vaccinated people appear to be infectious for a shorter period.
Previous variants typically produced less viral load in the body of infected fully vaccinated people, but the delta variant produces the same high amount of viral load in both unvaccinated and fully vaccinated people.
Effectivity of vaccines against delta
In one recent study, infection rates in India were analyzed which showed the BNT162b2 (Pfizer-BioNtech) and ChAdOx1 nCoV-19 (Oxford-AstraZeneca) vaccines were effective against the delta variant. Data on all symptomatic sequenced cases of Covid-19 in England were used to estimate the proportion of cases with either variant according to the patients’ vaccination status. The effectiveness after one dose of vaccine (BNT162b2 or ChAdOx1 nCoV-19) was notably lower among persons with the delta variant than among those with the alpha variant. The results were similar for both vaccines.
With the Pfizer vaccine, the effectiveness of two doses was 93.7% among persons with the alpha variant and 88.0% among those with the delta variant.
With the ChAdOx1 nCoV-19 vaccine, the effectiveness of two doses was 74.5% among persons with the alpha variant and 67.0% among those with the delta variant.
Only modest differences in vaccine effectiveness were noted with the delta variant as compared with the alpha variant after the receipt of two vaccine doses. Absolute differences in vaccine effectiveness were more marked after the receipt of the first dose. This finding would support efforts to maximize vaccination with two doses among vulnerable populations. (study was funded by Public Health England)
Vaccines available in the US
Vaccines in the US are highly effective, including against the delta variant – Pfifzer especially showing to be 88% effective after two doses.
Vaccines reduce a person’s risk of contracting COVID-19, including the delta variant. The COVID-19 vaccines authorized in the United States are highly effective at preventing severe disease and death, including against the delta variant. They are not 100% effective, and some fully vaccinated people will become infected (called a breakthrough infection) and experience illness. For such people, the vaccine still provides them strong protection against serious illness and death.
Given what we know about the Delta variant, vaccine effectiveness, and current vaccine coverage, layered prevention strategies, such as wearing masks and social distancing, are needed to reduce the transmission of this variant
Conclusion
Vaccines are playing a crucial role in limiting spread of the virus and minimizing severe disease. Although vaccines are highly effective, they are not perfect and there will be vaccine breakthrough infections.
Millions of Americans are vaccinated, and that number is growing. This means that even though the risk of breakthrough infections is low, there will be thousands of fully vaccinated people who might become infected and able to infect others, especially with the surging spread of the delta variant.
Low vaccination coverage in many communities is driving the current rapid and large surge in cases associated with the Delta variant, which also increases the chances that even more concerning variants could emerge.
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Now we conclude our episode number 65 “Delta variant.” Harendra did a great job by presenting the most current evidence about this newer strain of SARS-CoV-2. Vaccinated people are not 100% protected against the delta variant but are more likely to get a mild disease and spread the virus for a shorter period. Vaccinations continue to be the best weapon we have against this destructive pandemic. Even without trying, every night you go to bed being a little wiser.
Thanks for listening to Rio Bravo qWeek. If you have any feedback about this podcast, contact us by email RBresidency@clinicasierravista.org, or visit our website riobravofmrp.org/qweek. This podcast was created with educational purposes only. Visit your primary care physician for additional medical advice. This week we thank Hector Arreaza and Harendra Ipalawatte. Audio edition: Suraj Amrutia. See you next week!
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References:
Delta Variant: What We Know About the Science. Centers for Disease Control and Prevention, updated on August 26, 2021. https://www.cdc.gov/coronavirus/2019-ncov/variants/delta-variant.html.
Lopez Bernal J, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S, Stowe J, Tessier E, Groves N, Dabrera G, Myers R, Campbell CNJ, Amirthalingam G, Edmunds M, Zambon M, Brown KE, Hopkins S, Chand M, Ramsay M. Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. N Engl J Med. 2021 Aug 12;385(7):585-594. doi: 10.1056/NEJMoa2108891. Epub 2021 Jul 21. PMID: 34289274; PMCID: PMC8314739. https://pubmed.ncbi.nlm.nih.gov/34289274/
