Coronavirus Research Tracking - 3 September - Non-vaccine edition
Mask effectiveness, droplet dynamics, long Covid risk, wastewater tests, newer variants
This week we again have separate issues on vaccine and non-vaccine papers.
Non-vaccine research this week includes a very large mask trial, underestimating risks from coughing, no increased infection risk for people with some inflammatory conditions, increased risk of kidney problems associated with long Covid, the effectiveness of wastewater testing, and uncertainty over risks of two variants.
The tracker is shared with the COVID-19 Vaccine Media Hub.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
A large randomised study in Bangladesh has demonstrated the effectiveness of mask wearing. Symptomatic infections in the mask wearing villages was 9% lower than in the control villages, when variables were taken account of. In villages with surgical masks, infection levels tended to be lower than in villages supplied with cloth masks.
The study compared villages who received masks, information about mask wearing, and follow-up reminders with villages who did not. Mask wearing in villages with no intervention was 13.3%, compared with 42.3% in villages that received support for mask wearing.
Mask wearing declined over time but five months after the interventions the latter villages still had mask wearing levels 10% higher than the control villages. The paper has not yet been peer reviewed.
Coughs and sneezes spread diseases
The infection risk posed by droplets coming from coughs and sneezes may be higher than currently estimated. This study visualises where and for how long these droplets are found, and how temperature and humidity affects the droplets.
Monoclonal antibody therapy phase 3 trial success
AstraZeneca is reporting success for a monoclonal antibody treatment (currently called AZD7742) that reduces the risk of developing symptomatic Covid-19 in at-risk people. The dual antibody treatment was given to immunocompromised and chronically ill adults before infection, and reduced the symptomatic infection risk by 77%.
Five thousand participants were involved in the Phase 3 trial. AstraZeneca estimates that the treatment may remain effective for up to 12 months. A scientific paper has not yet been prepared describing the results. An earlier trial of this therapy did not demonstrate that it was effective when given after infection.
No increased risk of infection for people with some inflammatory conditions
A review of research found that having inflammatory arthritis or inflammatory bowel diseases does not increase the risk of developing Covid-19. There is some evidence that cytokine inhibitors used to treat these conditions can reduce the risk of developing severe Covid-19. However glucocorticoid drugs may increase the risk.
People with these inflammatory conditions do not seem to be at an increased risk of adverse vaccine side effects, or substantially reduced vaccine effectiveness. The paper was published in The Lancet Rheumatology.
Long lasting antibodies
Antibodies from natural SARS-CoV-2 infections can persist for at least 10 months, a new study reports. Earlier research had identified durability for 6-to-8 months. The research is based on a relatively small number of healthcare workers, and their demographic profile differed from the general population. The paper was published in JAMA Network Open.
Long Covid can increase risk of kidney damage
People who have longer lasting Covid-19 are at greater risk of developing several kidney dysfunctions or diseases. Depending on the specific kidney condition, risk increased between 50 and 100%, compared to those who did not experience long Covid. Risks increased in relation to severity of the Covid-19 symptoms. This is likely to place additional strain on healthcare. Study participants tended to be older white males, so the results may not be generalisable. The paper was published in the Journal of the American Society of Nephrology.
Effectiveness of wastewater testing
An ESR study concludes that wastewater testing can be a reliable and sensitive method for testing for community infections, even when infection rates are low. Modelling indicates that if just 10 people out of 100,000 are shedding the virus there is a high likelihood of viral RNA detection in the wastewater from that community. However, the pattern of shedding virus (such as high or consistent) from infected people, and whether they are symptomatic or asymptomatic can affect the likelihood of detection.
When infection levels are very low, the risk of false negative results (not detecting the virus) in wastewater increases. Sensitivity increases when wastewater testing is done at buildings rather than at the treatment plant. Further research is needed on the best sampling frequency at wastewater facilities. The paper has not yet been peer reviewed.
Limited mutational options for Delta
A study modelling the spike protein receptor binding domain structure proposes that the likelihood of the Delta variant developing mutations to escape vaccine control is slightly less than that for the wild type virus. The risk of evasion was calculated to be higher for the Gamma variant.
The authors conclude that there are limited opportunities for the virus to mutate in a way that makes vaccines ineffective. A limitation of the study is that sites outside of the receptor binding domain were not modelled and could have some effect.The paper has not yet been peer reviewed.
A variant called C.1.2, first identified in South Africa, has a range of mutations that potentially could increase transmissibility and/or immune evasion. However, this has not yet been demonstrated and further research is needed to establish if it is a cause for concern. The paper has not yet been peer reviewed.
A Twitter thread from the WHO Covid-19 Technical Lead notes that while this variant was identified in May, it is not common nor does it appear to be rapidly increasing in frequency. As research on other variants has shown (see 25 June Tracker), interactions between different mutations in a virus can lead to reduced transmission or immune evasion in actual infections.
The WHO provides information on how it classifies variants.
While the WHO has declared Mu (B.1.621) a variant of interest, its incidence has declined, as illustrated by information at Outbreak.info.
The Science Media Centre has an Expert Q&A on viral variants.