An infection may provide immunity for several years

A UK study estimates that previously infected people may have good protection from reinfection for at least 1.5 years. Antibody levels were assessed in over 7,000 people, and a model developed that estimated an average anti-spike IgG antibody half-life of about 6 months. Peak antibody levels were estimated to be 7-fold higher than the level needed for 50% protection.

About one quarter of participants did not develop antibodies after an apparent infection. This was reduced down to 11% when a more stringent rule for infection was applied. These were generally older people with low viral loads. The paper was published in Nature Communications.

Effect of Covid on cognition

Two initial papers from a “COVID and Cognition study” describe cognitive and memory problems for those with long Covid. The study will follow participants for one to two years.

The study is based on 366 participants, half of whom reported Covid symptoms and half who reported none. The objective of the study was not to estimate prevalence of long Covid since there were biases in who was recruited into the study.

Self-reported assessments of symptoms and severity were used along with online cognitive tests. The authors recognised a design flaw in not asking those who reported no Covid symptoms or no persistent symptoms if they had symptoms currently. This will be corrected in subsequent follow-ups.

The first paper reports that severity of early neurological and fatigue symptoms, combined with subsequent neurological, gastro-intestinal, and cardiopulmonary symptoms were good predictors of cognitive difficulties. Over half who reported long Covid stated that they had long periods where they were unable to work.

The second paper reports that cognitive deficits based on tests correlated with self-reported symptoms. Fatigue and/or systemic symptoms during the initial illness and ongoing neurological symptoms were predictive of performance on the cognitive tests.

Neither paper has yet been peer reviewed.

Oral protease inhibitor shows promise as a treatment

A protease inhibitor was found to be an effective antiviral oral treatment in mice. It limited weight loss and reduced lung damage in animals infected with SARS-CoV-2. Tests on cell lines, mice and macaques indicated it has a good safety profile in mammals. The inhibitor has the potential to work against a broad range of coronaviruses. Further clinical testing is underway. The paper was published in Science.

An antibody may be effective against a range of coronaviruses

A human antibody is able to neutralise a variety of coronaviruses. The antibody binds strongly to highly conserved parts of the receptor binding domain.

When given to mice the antibody prevented infections or reduced tissue damage  and weight loss when given after infection with the Beta variant. The authors suggest that the region the antibody binds to could be a good target for a universal coronavirus vaccine. Further animal and human trials are required. The paper was published in Science Translational Medicine.

Viral proteins associated with vascular problems

Several viral proteins may be responsible for increased risks of heart attacks and strokes following infection. The proteins increase permeability in the vascular system through affecting endothelial cells. ​​The study tested the proteins on cultured umbilical vein endothelial cells. It looked at the effect of individual proteins not combinations, and did not test the effect of the complete virus. The paper was published in eLife.

Infections probably grossly underestimated early in the pandemic in Europe and the US

A modelling study estimated that community transmission in parts of Europe and the US was likely in January 2020, before cases were reported. In March 2020 it is also possible that only 1-3% of infections were detected by surveillance programs.

Travel was found to be a key driver of infection spread, and the sources changed quickly resulting in travel restrictions lagging behind new sources. By July 2020 there was great variability in infection attack rates between countries in Europe and states within the US. The paper was published in Nature.

Infection levels in developing countries still poorly known

The burden of Covid-19 is far higher in developing countries, a meta-analysis has found. Seroprevalence is usually markedly higher than in more developed countries, but not at what are considered herd immunity levels.

Reported infection fatality rates could be up to 2.5 times higher than in developed countries. In developing countries the prevalence of Covid antibodies is often similar in younger and older age groups. The authors advocate for better vaccine distribution to low income countries. The meta-analysis includes few studies from Africa or Southeast Asia. The paper has not yet been peer reviewed.

Stringent infection controls and surveillance in schools lead to low transmission rates

Weekly screening of staff and students for asymptomatic cases in a US school found low rates of infections and in-school transmissions when rigorous mitigation strategies were in place. At-home saliva tests were used. Weekly screening was expensive and required substantial time from staff and volunteers. The school was in an affluent, mainly white community so the study will not be generalisable.

The school had mandatory masking, and student desks were at least 6 feet apart. Some of the mitigation practices in place included minor structural changes to improve airflow in the main school office, providing additional space for eating, and implementing one way pedestrian flows in high traffic areas.  The paper was published in Cell Reports Medicine.

White-tailed deer as a potential viral reservoir

SARS-CoV-2 infections appear to be relatively common in White-tailed deer in a US state. One-third of nearly 300 wild or captive deer had infections, with sequence and geographic data indicating both human-to-deer and deer-to-deer transmission.  Incidence in deer was higher during the hunting season, suggesting infections from hunters. The results indicate that the deer are, or may become, a reservoir for the virus. Evidence of deer-to-human transmission was not reported. The paper has not yet been peer reviewed.

‍

Subscribe to SMC-NZ's Coronavirus Research Tracker.