Mix-n-match COVID-19 vaccine boosters may result in fewer infections
People who received a different brand of COVID-19 vaccine booster than they did in the primary series had lower rates of infection than those who received the same brand, according to a study in Singapore published late last week in JAMA.
The study also found that participants who received a booster of any vaccine brand after the primary Pfizer/BioNTech series had lower rates of severe COVID-19 than did their unboosted peers. In a similar study earlier last week, US scientists writing in the New England Journal of Medicine found better booster protection only among those who initially received the Johnson & Johnson COVID vaccine.
The Singapore team analyzed rates and severity of COVID-19 infections among participants 60 years and older from Sep 15 to Oct 31, 2021, amid a surge of cases that the authors said was related to the relaxation of public health measures. In response to the surge, that age-group was invited to receive a Pfizer or Moderna vaccine booster.
Of 703,209 eligible people, 576,132 received boosters; 59% of them were 60 to 69 years old, 29% were 70 to 79, 11% were 80 and older, with 53% were women.
The incidence of COVID-19 infection and severe disease among participants who received Pfizer for both their primary series and booster (homologous vaccination) were 227.9 and 1.4 per million person-days. In contrast, the incidence of infection and severe disease among those receiving a different booster (heterologous) were 147.9 and 2.3 cases per million person-days, respectively, with incidence rate ratios (IRRs) of 0.18 (95% confidence interval [CI], 0.14 to 0.23) and 0.08 (95% CI, 0.01 to 0.56).
For recipients of a homologous Pfizer series, the incidence of infection and severe COVID-19 were 0.27 (95% confidence interval [CI], 0.26 to 0.29) and 0.05 (95% CI, 0.03 to 0.08), respectively. Among recipients of three Moderna doses, the incidence of infection was 133.9 cases per million person-years (IRR, 0.20; 95% CI, 0.14 to 0.27).
Rates of infection and severe illness among participants who received two doses of Pfizer vaccine but no booster were 600.4 and 20.5 per million person-days, respectively.
The authors write that the data "suggest that heterologous boosting may provide greater protection against COVID-19."
Feb 11 JAMA research letter
UK confirms third imported Lassa case, which proved fatal
British health officials late last week confirmed a third Lassa fever case in a patient with a suspected infection who has died, bringing the confirmed number in a family cluster to three.
In a statement, the UK's Health Security Agency (HSA) said it is contacting people who had contact with the family members before they were diagnosed for assessment, support, and advice. It also said the risk to the public remains low.
The two earlier cases and the probable case were announced last week and involved members of the same family in eastern England who had recently traveled to West Africa, where the viral hemorrhagic disease is endemic. One patient has recovered and another is being treated at Royal Free London hospital.
Lassa virus spreads by household items or food contaminated with urine or feces of infected rats. It can also spread among humans through infected body fluids. Imported cases occur sporadically outside of West Africa, with the United Kingdom reporting its last cases in 2009 and the United States reporting its last case in 2015.
Feb 11 UK HSA statement
Feb 9 CIDRAP News scan
H5N1 avian flu hits more poultry in Africa and Europe
Three countries—Cameroon, Denmark, and Romania—reported new highly pathogenic H5N1 avian flu outbreaks in poultry, according to the latest notifications from the World Organisation for Animal Health (OIE).
Cameroon's outbreak, its first since 2017, began on Jan 29 at a layer farm in the country's West region, killing 11,984 of 13,513 susceptible birds. Officials said the layer birds were kept in buildings that have an automatic watering system. So far, the source of the virus isn't known.
In Europe, Denmark reported another H5N1 event that started on Feb 10 at a layer farm in Zealand region, killing 400 of 800 birds. The rest were culled to contain the spread of the virus. And Romania'sn outbreak began on Feb 10 in backyard poultry in Ialomita County in the southeast, killing 49 of 65 birds.
Feb 13 OIE report on H5N1 in Cameroon
Feb 11 OIE report on H5N1 in Denmark
Feb 14 OIE report on H5N1 in Romania