Coronavirus Research Tracking - 10 December - Non-vaccine edition
Coronavirus Research Tracking - 10 December - Non-vaccine edition
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Non-vaccine papers this week include the risk to the baby when the mother has Covid-19 while pregnant, viral loads as an indicator of infectiousness, the effectiveness of masks, and the evolution of the virus.
Non-vaccine papers this week include the risk to the baby when the mother has Covid-19 while pregnant, viral loads as an indicator of infectiousness, the effectiveness of masks, and the evolution of the virus.
Publication
What our experts say
Context and background
Resources
Non-vaccine-related papers
Risk of disrupted immune system in babies when mother has Covid-19 while pregnant
Babies born after their mother became infected with SARS-CoV-2 during pregnancy did not appear to become infected. However, the risk of immunological perturbations was higher in comparison to babies from uninfected mothers.
For example, some interleukins and T cell types were at higher levels in babies from infected mothers, which could result in an imbalance between pro- and anti-inflammatory cytokines. Such babies may be at greater risk of developing inflammatory conditions when they get older, and this requires further study.
Data from the study also indicates that it may be best to vaccinate pregnant women in the second or early in the third trimester, when protective antibodies would be passed to their baby. The paper was published in Nature Immunology.
Viral load as an indicator of infectiousness
Viral load in the upper respiratory tract can be a good indicator of individual infectiousness, according to a model of viral dynamics. The logarithmic value of viral load is a more reliable predictor than the simple viral load value. The model could be useful for assessing the effect vaccines, other therapies and nonpharmaceutical interventions have on infectiousness.
The model also indicates that frequent antigen testing (every 1 to 3 days) can be as accurate as less frequent PCR testing, although there will be more false negative results due to the larger number of tests.
The model is based on data from people who were asymptomatic or had only mild infections and who quickly recovered. The paper was published in the Proceedings of the National Academy of Sciences.
Masks are better at preventing infection than just social distancing
Compared to social distancing, face masks can provide more effective protection from infection, even when the mask is not a perfect fit. However, this applies only if everyone wears a mask. This conclusion is based on modelling particle sizes and flow physics and interactions between two people.
Social distancing (up to 3 metres) without a mask may still result in up to a 90% risk of infection after a few minutes. Depending on the type of mask and snugness of fit, the risk can fall to as low as 0.4%. As found in previous studies, FFP2 or N95 masks were more effective than surgical masks. The study examined different combinations of masks and degree of fit. The paper was published in the Proceedings of the National Academy of Sciences.
Identifying mutations that can enable immune evasion
A study of the virus’ receptor binding domain identified a range of mutations that could enable it to escape antibody responses. Combinations of mutations can make the virus more resistant to monoclonal antibodies, as well as natural and vaccine-induced immune responses without affecting infection ability.
The research was done in part using pseudoviruses, and does not take account of how mutations in the receptor binding domain may influence, or be influenced by, mutations elsewhere in the virus. However, the research can help inform development of new therapies that reduce the risk of immune evasion. The paper was published in Science.
Evolution of the virus in an immunocompromised patient
A prolonged Covid-19 infection in a patient with HIV resulted in a viral variant with features and properties of both the Beta and Delta variants. This occurred before either variant emerged, providing support for the hypothesis that prolonged infection in immunosuppressed patients can facilitate the development of new variants.
The patient was infected for six months, but was largely asymptomatic for Covid-19 despite high viral loads. This may have been due, the authors suggest, to the HIV treatment reducing anti-inflammatory responses, although other factors may also explain the lack of symptoms. The paper has not yet been peer reviewed.
Possible next steps for viral evolution
A news report in Nature discusses how the virus has evolved so far, and possible future developments. At some point transmissibility will not be able to increase further, but how much it can still increase is uncertain. There are a range of ways that the virus could evolve, and will depend on how we handle its spread.
Non-vaccine-related papers
Risk of disrupted immune system in babies when mother has Covid-19 while pregnant
Babies born after their mother became infected with SARS-CoV-2 during pregnancy did not appear to become infected. However, the risk of immunological perturbations was higher in comparison to babies from uninfected mothers.
For example, some interleukins and T cell types were at higher levels in babies from infected mothers, which could result in an imbalance between pro- and anti-inflammatory cytokines. Such babies may be at greater risk of developing inflammatory conditions when they get older, and this requires further study.
Data from the study also indicates that it may be best to vaccinate pregnant women in the second or early in the third trimester, when protective antibodies would be passed to their baby. The paper was published in Nature Immunology.
Viral load as an indicator of infectiousness
Viral load in the upper respiratory tract can be a good indicator of individual infectiousness, according to a model of viral dynamics. The logarithmic value of viral load is a more reliable predictor than the simple viral load value. The model could be useful for assessing the effect vaccines, other therapies and nonpharmaceutical interventions have on infectiousness.
The model also indicates that frequent antigen testing (every 1 to 3 days) can be as accurate as less frequent PCR testing, although there will be more false negative results due to the larger number of tests.
The model is based on data from people who were asymptomatic or had only mild infections and who quickly recovered. The paper was published in the Proceedings of the National Academy of Sciences.
Masks are better at preventing infection than just social distancing
Compared to social distancing, face masks can provide more effective protection from infection, even when the mask is not a perfect fit. However, this applies only if everyone wears a mask. This conclusion is based on modelling particle sizes and flow physics and interactions between two people.
Social distancing (up to 3 metres) without a mask may still result in up to a 90% risk of infection after a few minutes. Depending on the type of mask and snugness of fit, the risk can fall to as low as 0.4%. As found in previous studies, FFP2 or N95 masks were more effective than surgical masks. The study examined different combinations of masks and degree of fit. The paper was published in the Proceedings of the National Academy of Sciences.
Identifying mutations that can enable immune evasion
A study of the virus’ receptor binding domain identified a range of mutations that could enable it to escape antibody responses. Combinations of mutations can make the virus more resistant to monoclonal antibodies, as well as natural and vaccine-induced immune responses without affecting infection ability.
The research was done in part using pseudoviruses, and does not take account of how mutations in the receptor binding domain may influence, or be influenced by, mutations elsewhere in the virus. However, the research can help inform development of new therapies that reduce the risk of immune evasion. The paper was published in Science.
Evolution of the virus in an immunocompromised patient
A prolonged Covid-19 infection in a patient with HIV resulted in a viral variant with features and properties of both the Beta and Delta variants. This occurred before either variant emerged, providing support for the hypothesis that prolonged infection in immunosuppressed patients can facilitate the development of new variants.
The patient was infected for six months, but was largely asymptomatic for Covid-19 despite high viral loads. This may have been due, the authors suggest, to the HIV treatment reducing anti-inflammatory responses, although other factors may also explain the lack of symptoms. The paper has not yet been peer reviewed.
Possible next steps for viral evolution
A news report in Nature discusses how the virus has evolved so far, and possible future developments. At some point transmissibility will not be able to increase further, but how much it can still increase is uncertain. There are a range of ways that the virus could evolve, and will depend on how we handle its spread.
