Welcome to our weekly roundup of developments from the coronavirus pandemic.
Exposed children are less likely to be infected than adults
Ahead of the planned reopening of English schools to some classes on 1 June, a large systematic review has suggested that children and adolescents under the age of 20 are much less likely than adults to become infected with Covid-19. A team at University College London analysed data from 18 studies that traced the contacts of infected individuals, which put children’s risk of being infected at 56% lower than adults when in contact with an infected person.
The analysis suggests that children have played a smaller part than adults in spreading the virus in the population, but the evidence for the finding is weak and there has still not been enough research to determine whether infected children are less likely than adults to spread the virus to others. Meanwhile, an independent group of UK scientists has warned that reopening schools could lead to a surge of community infections, saying that current infection levels and the lack of a well-established contact-tracing system make reopening schools too risky.
More evidence for asymptomatic cases
More that two-thirds of people in England who tested positive for Covid-19 outside hospitals and care homes showed no symptoms at the time of the test or in the week before or after, according to research by the Office for National Statistics (ONS). The national snapshot infection survey, found that around 80% of those who tested positive reported no symptoms at the time of testing and 70% were also asymptomatic in the week before and after being swabbed.
The findings are consistent with previous studies, including testing of pregnant women in a New York hospital and tests of passengers and crew onboard the Diamond Princess cruise liner docked in Japan. The ONS analysis also found that, of those reporting Covid-19-specific symptoms (cough, fever, or loss of taste or smell) on the day of testing, just under 7% tested positive for Covid-19. According to the ONS, the figures highlight the importance of social distancing to restrict the spread of the virus, and also underline the challenges that could be faced by tracking and tracing any new infections that occur as lockdown is eased.
Who should shield from Covid-19?
As many are enjoying the gradual easing of restrictions, allowing some aspects of everyday life to resume, those in the UK who are at extremely high risk – cancer patients, those with immune and other serious health conditions – are being asked to remain in lockdown. Some have complained of feeling demoralised and forgotten. An editorial in this week’s British Medical Journal, by David Spiegelhalter and George Davey Smith, advocates replacing the current binary approach with a graded risk score for “getting infected and then dying from the infection”, which would determine the extent to which people would self-isolate. On the basis of factors including age, sex, underlying health issues, ethnicity and postcode (which gives information on both socio-economic factors and local risk of infection), people could be assigned to one of five categories – for example, from very low to very high risk, the scientists suggest.
“Lockdown is seriously damaging many aspects of people’s lives, harming most those with the least resources,” the authors write. “As constant vigilance will be required over the coming months and perhaps years, serious consideration should be given to implementing locally informed and implemented strategies to stratify shielding according to risk.”
Science Weekly podcast
In this week’s edition of Science Weekly, Sarah Boseley speaks to Prof Susan Lanham-New about whether vitamin D could have a role in protecting us from Covid-19
Plasma trial expanded to thousands of patients
Hospitals in England announced the expansion of a trial of blood plasma transfusions from recovered Covid-19 patients this week, to learn whether the antibody-rich serum could help combat the disease. So far, only small numbers of severely ill patients in UK intensive care units have been treated with convalescent plasma, but the transfusions are thought to be more effective if used earlier. Recent results from a trial at Mount Sinai hospital in New York City found that patients who received plasma were more likely to survive, and that those treated before being put on a mechanical ventilator in intensive care appeared to benefit most.
The NHS blood and transplant service (NHSBT) said its clinical trial unit had this week begun collaborating with the Oxford-led Recovery trial with the aim of getting convalescent plasma into thousands of people in hospital with coronavirus in England. All patients in hospital with Covid-19, rather than just the most critically ill, will be eligible for a serum transfusion provided they have no medical conditions or allergies to blood products that could put them at risk. NHSBT is actively seeking donors who have recovered from Covid-19 to give blood to be used in the trial.
