Silver Bullet July 23 - Mixed signals on masks, viral origins and evolution
A weekly update on all things COVID-19. News, public health guidance, trends, breakthroughs, and thousands of scientific papers distilled down to what you need to know right now.
Confused? You’re not alone.
COVID-19 cases are down in many parts of the country, and the CDC has said that fully vaccinated people no longer need to wear a mask. At the same time, the Delta varian is spreading rapidly, with alarming rises in cases in some states including Florida, Missouri, and Arkansas—but almost exclusively among unvaccinated people. Adding to the confusion, the World Health Organization says vaccinated people should continue wearing masks. Are we past the worst of it or not? Is it time yet to relax, or are we headed back into lockdown?
Dr. Ashish K. Jha, dean of the Brown University School of Public Health, tackled this question in an Opinion piece for the Boston Globe. It’s worth reading the entire piece, but here are a few of the highlights.
First, if you are fully vaccinated, you are still 90% less likely to be infected by the Delta variant, and you are highly unlikely to have severe illness. However, Jha points out that 90% is not 100%. “If a vaccinated person encounters the virus repeatedly or in high enough concentrations, the chances of a breakthrough infection gets more substantial.”
And in many places in the world, including some parts of the US, vaccination rates are still not high enough to prevent the extremely rapid spread of the Delta variant. That’s the basis of the WHO’s recommendation to continue masking. Ultimately, Jha explains, we are at a point where no single set of recommendations will be right for every region or every state.
“As we wind our way through this pandemic, we are now entering a phase where guidance will — and should — be local and will change as the realities on the ground change,” writes Jha. “The evidence right now says if you live in a highly vaccinated community with low infection rates, fully vaccinated people can skip the mask if they are willing to tolerate a minuscule risk of a breakthrough infection. For people who live in low vaccination, high infection communities, the choice is different: Mask up indoors or be willing to accept a far more meaningful risk of getting the virus.”
Vaccines remain effective against delta variant
A new study in The New England Journal of Medicine confirms that the Pfizer-BioNTech and AstraZeneca COVID-19 vaccines are effective against the Delta variant and other variants of the virus. (Other vaccine brands were not included in this study.) The Pfizer-BioNTech vaccine was 93.7% effective after two doses against the alpha variant (B.1.1.7) and 88% effective against the delta variant. Two doses of the AstraZeneca vaccine was 74.5% effective against alpha and 67% effective against delta. However, the differences are greater for partially vaccinated people. One dose of either vaccine was just 30.7% effective.
CDC releases school guidance for fall 2021
In a new set of guidelines, the CDC is encouraging in-person learning for schools starting in fall 2021, citing “widespread availability of safe and effective COVID-19 vaccines for people 12 and older,” as well as downward trends in cases, hospitalizations, and deaths. (Trends which have started to turn upward again since the July 9 statement.) The agency still recommends masks for anyone age 2 and older who is not vaccinated, and calls for three feet between student desks. Layered prevention strategies are recommended, because many students are too young to be vaccinated. “Screening testing, ventilation, handwashing and respiratory etiquette, staying home when sick and getting tested, contact tracing in combination with quarantine and isolation, and cleaning and disinfection are also important layers of prevention to keep schools safe.”
Vaccines vs viral evolution
One of the concerns about the COVID-19 pandemic is that a sluggish vaccine rollout may exert selective pressure on the virus, encouraging the evolution of vaccine-resistant variants. Reassuringly, a new analysis of 1.8 million SARS-CoV-2 genomes from 183 countries shows a decline in diversity of viral lineages is correlated with increases in mass vaccination. The study also found that sections of the viral genome affected by B cell immunity were mutating more rapidly than those related to T cell immunity, reflecting selective pressure exerted by vaccines. “This study presents the first known evidence that COVID19 vaccines are fundamentally restricting the evolutionary and antigenic escape pathways accessible to SARS-CoV-2. The societal benefit of mass vaccination may consequently go far beyond the widely reported mitigation of SARS-CoV-2 infection risk and amelioration of community transmission, to include stemming of rampant viral evolution.” This study is not yet peer-reviewed.
Breakthrough infections sicken six at outdoor wedding, one dead
At an outdoor wedding in Texas where all guests were vaccinated, six vaccinated individuals were infected with the Delta SARS-CoV-2 variant. Three males and three females between 53 and 69 years old were infected. The index cases were a man and woman who traveled from India for the wedding and had tested negative for SARS-CoV-2 by qPCR. The man from India became seriously ill and later died. One patient who received the Pfizer-BioNTech vaccine developed severe symptoms and was hospitalized. This study is published as a preprint and has not been peer-reviewed.
Bat study points to natural origin of SARS-CoV-2
In a letter in Cell Host and Microbe, Canadian zoonotic virus expert Arinjay Banerjee highlights the recent work of Zhou, et al (Cell, 2021) in tracking down the evolutionary origins of SARS-CoV-2. In that study, the researchers studied samples from 411 bats from Yunnan province in China collected between May 2019 and November 2020. They identified seven relatives of the SARS-CoV-2 virus, four of them novel. Of the four novel viruses, one identified as RpYN06 is the closest relative of SARS-CoV-2 yet known, after RaTG13, according to Banerjee. RaTG13 is 96.1% identical to SARS-CoV-2 and RpYN06 is 94.48% identical. However, RpYN06 has higher sequence identity to SARS-CoV-2 for some individual genes. Says Banerjee, “While debate on the origin of SARS-CoV-2 continues, this recent study by Zhou et al., 2021 further bolsters the natural existence of SARS-CoV-2-related viruses in Rhinolophus bats.”
Other science news
Report advises limits on sushi consumptions, especially tuna
A study from Spain looked at arsenic and heavy metals in sushi in adults, teens, and children, and concluded that while sushi is a healthful and highly nutritious food, meals of sushi should be limited to remain below critical exposure levels for arsenic, methylmercury, and other contaminants. For an 8-piece adult portion, the safest choices were salmon and eel. Including tuna caused the meal to exceed a safe daily intake of methylmercury. The safe portion size for children was 3 pieces. (Note: most people do not eat sushi every day, and thus probably average far less than 8 pieces/day overall.)
Plant-based diet reduces menopause symptoms
A plant-based diet rich in soy reduces hot flashes by 84%, according to a new study in Menopause. Over the course of the 12 week study, 60% of women became completely free of moderate-to-severe hot flashes. Overall, hot flashes decreased 79%.
Could COVID shots in secret lure holdouts? by Jennifer Henderson, MedPage Today
Italy said it will require proof of vaccination or a negative test for many social activities by Emma Bubola, The New York Times