Previous COVID infection may confer 56% protection against reinfection
A study in Qatar estimates that previous COVID-19 infection imparts 56% protection against future symptomatic infection caused by the highly transmissible Omicron variant, down from about 90% for other SARS-CoV-2 strains.
The study, published yesterday in the New England Journal of Medicine (NEJM), was led by researchers at Weill Cornell Medicine–Qatar in Doha.
The team extracted data on COVID-19 testing, vaccination, clinical infections, outcomes, and demographics from national databases amid the Omicron surge.
The median interval between initial COVID-19 infection and polymerase chain reaction (PCR) testing of 5,696 positive cases and 10,673 negative controls was 279 days for analysis of the Alpha variant, 285 days for the Beta variant, 254 days for the Delta variant, and 314 days for Omicron.
Estimated effectiveness of a previous infection in preventing reinfection was 90.2% against Alpha, 85.7% against Beta, 92.0% against Delta, and 56.0% against Omicron. Sensitivity analyses that excluded vaccinated patients confirmed the results.
Among reinfected patients, one patient with the Alpha variant became severely ill, as did two each with Beta and Omicron, but no patients with Delta did so. No reinfection was critical or fatal. Estimated effectiveness against severe, critical, or fatal COVID-19 was 69.4% for Alpha, 88.0% for Beta, 100% with Delta, and 87.8% with Omicron.
"We found that the effectiveness of previous infection in preventing reinfection with the alpha, beta, and delta variants of SARS-CoV-2 was robust (at approximately 90%), findings that confirmed earlier estimates," the researchers concluded.
"Such protection against reinfection with the omicron variant was lower (approximately 60%) but still considerable," they added. "In addition, the protection of previous infection against hospitalization or death caused by reinfection appeared to be robust, regardless of variant."
Feb 9 NEJM research letter
Study: Third of US adults develop new symptoms post-COVID-19
Thirty-two percent of older adults who were diagnosed as having COVID-19 in 2020 developed a new symptom in the months following infection that required them to seek additional medical care, according to a study yesterday in BMJ.
The observational study was based on US health insurance plan records of 133,366 individuals aged 65 or older in 2020 who were diagnosed with COVID-19 before Apr 1, 2020. The cohort was matched and compared to adults from 2020 and 2019.
According to the authors, only 21% of non-COVID older adults from 2020 sought medical care during the same period, compared to 32% of adults with COVID-19; all medical care after 21 days of acute infection was included in the study.
Respiratory failure (risk difference 7.55, 95% confidence interval 7.18 to 8.01), fatigue (5.66, 5.03 to 6.27), hypertension (4.43, 2.27 to 6.37), memory difficulties (2.63, 2.23 to 3.13), kidney injury (2.59, 2.03 to 3.12), mental health diagnoses (2.50, 2.04 to 3.04), hypercoagulability (1.47,1.2 to 1.73), and cardiac rhythm disorders (2.19, 1.76 to 2.57) had the greatest risk differences compared with both the 2020 and 2019 comparison groups, the authors said.
Men, adults over 75, and Black COVID-19 patients were at the greater risk for developing new sequelae in the months following COVID-19 infection.
"These findings further highlight the wide range of important sequelae after acute infection with the SARS-CoV-2 virus," the authors concluded. "Understanding the magnitude of risk for the most important clinical sequelae might enhance their diagnosis and the management of individuals with sequelae after acute SARS-CoV-2 infection."
Feb 9 BMJ study
Launch of first human trial of Nipah virus vaccine announced
Public Health Vaccines (PHV), based in Massachusetts, yesterday announced the launch of a phase 1 clinical trial for its Nipah virus vaccine, the first of its kind to be tested in people.
The vaccine was developed by scientists at the National Institute of Allergy and Infectious Diseases, which licensed the product to PHV. The vaccine's development has been supported by the Coalition for Epidemic Preparedness Innovations (CEPI), which in 2017 flagged Nipah virus as one of four diseases that has the capability to trigger a major global epidemic.
The bat-borne virus can spread to both humans and livestock and can spread person-to-person. It is listed as a priority virus by the World Health Organization and as a category C bioterrorism agent by the US Centers for Disease Control and Prevention (CDC).
PHV's vaccine is a single-dose live, attenuated, recombinant vesicular stomatitis virus that expresses both the Nipah virus glycoprotein and the Ebola virus glycoprotein, which is required for receptor-based viral entry.
The phase 1 trial will assess safety, tolerability, and immunogenicity of three dose levels in 60 healthy adults in the United States. Pending favorable results, the company said in a news release that it will launch a phase 2 trial this year in a country where the disease is endemic.
Feb 9 PHV press release
CDC: Recent US H5N1 avian flu detections pose low threat to people
In the wake of recent highly pathogenic H5N1 avian flu detections in US waterfowl and the first related outbreak in poultry, the CDC said yesterday that the threat to the public remains low, but people who have greater exposure may have a heightened risk.
Recent sporadic H5 infections in people have been reported from abroad, including one in January in the United Kingdom in a patient who had close contact with poultry. Similar sporadic infections in the United States resulting from close contact with wild birds or poultry wouldn't be surprising and wouldn't change its risk assessment, the CDC added. Human-to-human spread of avian flu viruses is rare and hasn't led to sustained transmission.
The CDC said it has an existing candidate H5 vaccine virus that is nearly identical to the virus found recently in US wild bird samples, which could be used to make a vaccine for humans, if needed. It added that sequencing also suggests that the virus would be susceptible to current antiviral medications used to treat flu.
Feb 9 CDC statement
Feb 9 CIDRAP News story "H5N1 avian flu turns up in US poultry on Indiana turkey farm"