New antibody study in Spain adds evidence against herd immunity

The following is a brief roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for Covid-19, the illness caused by the virus.

Study may explain severity of Covid-19 in high-risk groups

A small study of high-risk Covid-19 patients may help explain why their health issues contribute to more severe cases of the illness. Chronic conditions like obesity, diabetes, liver disease, hypertension, and heart disease also cause inflammation. Researchers studied 16 Covid-19 patients with these conditions and found in all of them the enzyme caspase-1 and the inflammatory protein IL-18 - evidence of an immune-system process called the inflammasome, which leads to decreases in immune cells and a form of cell death called pyroptosis. On top of their pre-existing inflammation, inflammasome activation may be what brings on the "hyperinflammation" and immune dysfunction that makes these patients so severely ill, the researchers from MedStar Georgetown Transplant Institute (MGTI) in Washington, D.C. and SUNY Downstate Medical Center in Brooklyn suggested. Because the inflammasome plays a role in other viral infections, "there has been ... speculation about the inflammasome and SARS-CoV-2 for many months," coauthor Dr. Alexander Kroemer of MGTI told Reuters, adding that his team is the first to demonstrate an activated inflammasome in Covid-19 patients. These findings, published on Monday in the Journal of Hepatology, "help to explain why vulnerable patient groups are so severely affected by Covid-19," he said.

Herd immunity unlikely even in hardest hit countries

Spain was one of the countries hardest hit by the coronavirus pandemic. But even there, only 5% of the population has antibodies proving prior infection by the virus, according to a nationwide study of more than 60,000 people using two different tests to try to assure accuracy. To achieve herd immunity that would protect the uninfected, 70% to 90% of a population needs to be immune from an illness. Data from participants who ranged from infants to people in their 90s showed some variation by region but nowhere near levels needed for herd immunity. The prevalence of coronavirus antibodies was less than 3% in coastal regions, but more than five times higher in areas with major outbreaks. "Despite the high impact of Covid-19 in Spain, prevalence estimates remain low and are clearly insufficient to provide herd immunity," the study authors reported on Monday in The Lancet. "In this situation, social distance measures and efforts to identify and isolate new cases and their contacts are imperative for future epidemic control."

Only certain patients likely to benefit from antibody-rich plasma

Doctors may need to be more selective about who to treat with blood plasma from recovered Covid-19 patients, with a preference toward those whose symptoms have just begun, new research suggests. Researchers have been testing whether infusions of antibody-rich convalescent plasma can help Covid-19 patients recover faster. On Friday, investigators in The Netherlands said they stopped their convalescent plasma trial prematurely after only 86 hospitalized patients had been enrolled because nearly 80% were found to already have their own neutralizing antibodies. "These observations caused concerns about the potential benefit of convalescent plasma in the study population," the authors wrote in a paper posted on medRxiv in advance of peer review. Half of the patients in the study had been symptomatic for more than 10 days before being hospitalized. Given the high prevalence of neutralizing antibodies at hospital admission, they added, "screening for antibodies and prioritizing convalescent plasma to risk groups with recent symptom onset will be key to identify patients that may benefit from convalescent plasma."

Child abuse may be surging during pandemic, doctors warn

A new study from a UK hospital adds to evidence that domestic child abuse may be surging during the pandemic. Between late March, when the British lockdown started, and late April, the number of new cases of head injury likely caused by child abuse seen by doctors at that hospital rose nearly 15-fold compared with the same period the previous three years, researchers reported on Thursday in Archives of Disease in Childhood. During the study period, 10 babies, ages 17 days to 13 months, came to the emergency department with suspected abusive head trauma, whereas in past years the doctors were seeing roughly one such baby every couple of months. The infants' families all lived in areas of significant social and economic deprivation. The authors note that the socioeconomic and psychosocial challenges associated with the pandemic can increase parental stress. They warn that their data probably underestimates the scale of the problem. "The increase in incidence seen at our institution reflects a rise in domestic abuse in countries enforcing similar social distancing measures," they conclude. "This sobering figure is likely under-represented due to public avoidance of hospitals at this time."