Coronavirus Research Tracking - 27 May
Long covid, waning immunity, Omicron variants, hepatitis, antiviral therapies
This week, a large US study looks at whether vaccination reduces risks of long Covid, effectiveness of vaccination for cancer patients, and stronger immune responses against Omicron sub-lineages following an earlier infection and vaccination.
Unusual hepatitis cases in children appear linked to adenovirus, several papers on long Covid, the different symptoms associated with Omicron infections, and effectiveness of antiviral and monoclonal antibody therapies.
The Research Tracker is prepared by Dr Robert Hickson for the Science Media Centre.
New study comparing vaccine effectiveness in Africa
A study called the CoviCompare project has commenced. It will compare immune responses to different vaccines in people from France, Guinea, and Mali. The mRNA and Johnson & Johnson/Janssen vaccines are included in the project, but others are likely to be added later. A description of the project was published in Nature Medicine.
Vaccination may provide only modest protection from long Covid
A large study of US veterans found that prior vaccination confers partial protection against long Covid. The hazard ratio was 15% less than unvaccinated controls. Risk reduction was greater for those who had received mRNA vaccines, compared to those with the Johnson & Johnson/Janssen vaccine.
Over 30,000 participants with post-vaccination infections were included. Participants were mostly older men. The study was undertaken before the Omicron variants were common. The paper was published in Nature Medicine.
Vaccinated cancer patients at greater risk of infection than those without cancer
Vaccinated people with cancer can have a greater risk of being infected than vaccinated healthy adults. They were also more likely to be hospitalised and die than those without cancer. Overall, the increased infection risk was about 25% higher for cancer patients, and mortality risk nearly seven-fold greater. The infection risk varied for different types of cancer. Those with pancreatic, liver, or lung cancers had the greatest risk of post-vaccination infection.
Participants had either two mRNA doses, or a single Johnson & Johnson/Janssen vaccine. The paper was published in JAMA Oncology.
Hybrid immunity appears to wane more slowly
Immunity wanes more slowly in people who were infected and vaccinated than for those who were only vaccinated. Even one vaccine dose after an infection provided a higher level of reinfection protection than two doses without an infection.
Reinfections in recovered unvaccinated people occured at a rate of 10.5 per 100,000 between 4 and 6 months after the original infection. The rate increased to 30.2 after 12 months. For those with two vaccine doses, infection risk was 88.9 between 6 and 8 months after vaccination. For people who had an earlier infection followed by one vaccine dose the reinfection rate was only 11.6 between 6 and 8 months.
This Israeli study involved the Pfizer/BioNTech vaccine. The paper was published in the New England Journal of Medicine.
BA.4 & BA.5 have different antigenic properties than BA.1 and BA.2
The BA.4 and BA.5 sub-lineages have different antigenic properties than other Omicron types, especially BA.1. While post-vaccination sera showed similar neutralising ability against BA.1, BA.2, BA.4 and BA.5, sera from unvaccinated BA.1 or BA.2 infections had poor neutralisation activity against BA.4 & BA.5.
However, BA.1 and BA.2 infections after vaccination generated more broadly neutralising antibodies that neutralised BA.4 & BA.5. The paper has not yet been peer reviewed.
Atypical hepatitis in children
A UK study found that 68% of children with atypical hepatitis had an adenovirus infection, while only about 10% of cases had detectable SARS-CoV-2. This supports the hypothesis that such hepatitis cases are often linked to adenovirus infections. However, the nature of the adenovirus, and whether other factors are involved requires further research.
There have been 197 cases in children under 16 this year in the UK. The majority of cases involve jaundice and gastro-intestinal symptoms. Eleven needed liver transplants, but none have died. The paper is a technical briefing from the UK Health Security Agency.
Over half of 189 people who had Covid-19 had one or more persistent symptoms. Thirteen percent of controls also had long Covid-like symptoms (such as fatigue). Symptoms were clinically assessed, rather than based on self-reporting.
Those with long Covid reported a lower quality of life than other Covid participants and the controls. The virus was not detected in those with long Covid, indicating that persistence of the virus is not a cause. Other causes of the reported symptoms could also not usually be found.
Participants had mostly mild to moderate Covid symptoms and were not hospitalised. The paper was published in Annals of Internal Medicine.
A US analysis found that 20% of adults had health conditions that might be related to an earlier Covid infection. Conditions include neurological, heart, circulatory, kidney, respiratory and musculoskeletal problems. Forty five percent of those over 65 had subsequent health problems, and had a greater risk of developing neurological and mental health conditions. The paper was published in Morbidity and Mortality Weekly Report.
A Japanese study found that long Covid symptoms were less common in people who had had an Omicron infection. Based on interviews with 18 people with an Omicron infection, only one (ca. 5%) had persistent ongoing symptoms at least two months after the infection. This compared with 10 of 18 (55%) matched people infected with earlier variants.
The study was small, and there were different methodologies for surveying people with Omicron and other variant infections. Alternative causes for persistent symptoms could not be excluded. The paper has not yet been peer reviewed.
Another small study found that non-hospitalized Covid-19 patients continued to experience neurologic symptoms, fatigue, and compromised quality of life for more than a year after their initial infection. There were perceived improvements in their recovery, cognitive function, and fatigue, but quality of life did not significantly improve over the times since being infected. No significant difference was found with symptom persistence between vaccinated and unvaccinated participants, although the number of unvaccinated was small.
The study surveyed only 52 patients (27 with, and 25 without Covid) a median of 14.8 months after initial symptoms. Most of the participants were female, with a mean age of 43. The paper was published in the Annals of Clinical and Translational Neurology.
The New York Times has an article describing what is known about long Covid so far.
Omicron infections have different symptom profile than earlier variants
The UK REACT-1 study reports that people with Omicron infections have different symptoms than those seen from earlier variants. There is a lower reported loss of sense of smell and taste for Omicron, and higher reporting of cold-like and influenza-like symptoms.
Omicron BA.2 was associated with more symptoms than other variants, and greater disruption to daily activities than BA.1. People with BA.2 reported an average of 6 symptoms, compared with 4.6 for BA1 & Alpha, and 3.4 for Delta.
The study involved 1.5 million randomly selected people. The paper has not yet been peer reviewed.
A study in Hong Kong found that giving Paxlovid to hospitalised patients with BA.2 infections reduced the likelihood of them developing worse symptoms. Paxlovid patients had a quicker reduction in viral load, were less likely to die, and spent about a day less in hospital than matched controls.
Similar results were seen for patients given the antiviral molnupiravir, although Paxlovid was associated with lower mortality and a slightly shorter stay. Patients receiving oxygen were not included in the study. The paper has not yet been peer reviewed.
A monoclonal antibody is more effective than the antiviral molnupiravir
The monoclonal antibody sotrovimab proved to be more effective at preventing severe Covid than the antiviral molnupiravir. The risk of developing severe Covid or dying within one month for those receiving sotrovimab was half that of patients taking molnupiravir. Between two and three thousand patients were in each group. The paper has not yet been peer reviewed.