COVID Omicron variant shown to spread better in households than Delta
The SARS-CoV-2 Omicron variant is much more transmissible among household members than Delta, with an estimated secondary attack rate (SAR) from thrice-vaccinated index patients of 46%, compared with 11% for Delta, finds a study published today in Nature Communications.
The SAR is the percentage of contacts who become infected by an index (initial) patient.
Norwegian Institute of Public Health researchers used contact tracing data to track the 10-day SAR of Omicron and Delta among 1,122 index patients infected with Omicron (59%) or Delta (41%) and 2,169 household contacts (60% for Omicron primary cases and 41% for Delta) from December 2021 to January 2022. The data represented 8 of Norway's 11 counties.
The estimated overall Omicron SAR was 51%, compared with 36% for Delta. The SAR among thrice-vaccinated index patients was 46%, versus 11% for Delta (relative risk [RR], 1.41). Although the average SAR was lower for both variants among contacts vaccinated with three doses, transmission was higher with Omicron than Delta among all vaccination groups except one-dose recipients.
Both twice- and thrice-vaccinated index patients were at comparable risk as unvaccinated index patients of spreading Omicron to adult household contacts (RR, 1.04 and 0.99, respectively). In contrast, Delta index patients who received three vaccine doses were at an 82% lower risk of spreading Delta (RR, 0.18).
There were no significant differences in risk of infection by age-group, sex, or time since the last vaccine dose in twice-vaccinated contacts.
Vaccine effectiveness (VE) for thrice-vaccinated adult household contacts was lower for Omicron than Delta (45% vs 65%) and higher than that of twice-vaccinated contacts, who had 27% protection against Omicron infection and 42% against Delta.
"Our study indicates that the higher overall SAR among household contacts of Omicron cases is most likely due to higher intrinsic transmissibility of this variant and lower vaccine effectiveness," the researchers wrote.
"Contacts vaccinated with three doses had a lower risk of infection with Delta and Omicron, but our findings suggest that three-dose vaccinated cases with Omicron infection can spread effectively in households," they concluded.
Sep 29 Nat Commun study
Study suggests pandemic altered personalities in US
The pandemic may have altered the trajectory of personality across the United States, especially in younger adults, according to a study in PLOS One. The findings challenge the hypothesis that personality traits are independent of environmental factors.
To conduct the study, researchers from the Florida State University College of Medicine used longitudinal assessments of personality from 7,109 people enrolled in the online Understanding America Study to look at five personality factors from before the pandemic (May 2014 through April 2020), during the early part of the pandemic (March to December 2020), and the adaptation phase of pandemic (2021 and 2022). The five traits were neuroticism, extraversion, openness, agreeableness, and conscientiousness.
A total of 18,623 assessments, with a mean of 2.62 per participant, were analyzed. Respondents were roughly 42% male, and between the ages of 18 and 109. There were few changes between 2020 personality traits and those from 2014-2020, but significant changes between traits seen in 2021-2022 and pre-pandemic.
Neuroticism remained largely unchanged in all three periods, but extraversion, openness, agreeableness, and conscientiousness declined in 2021 through 2022 compared to their level pre-pandemic, the authors wrote. Young adults had the biggest changes in traits compared to older adults.
"Change in personality from before to during the pandemic was approximately one-tenth of a standard deviation. Although modest in absolute terms, it can be put in the perspective of developmental changes that occur over adulthood," the authors explained. "Normative personality change has been estimated to be approximately one-tenth a standard deviation per decade in adulthood."
Sep 28 PLOS One study
Qatar announces COVID test requirement for World Cup travelers
Ahead of World Cup soccer competition that begins in Qatar in the middle of November, tournament organizers today announced that visitors attending the event will need to test for COVID-19 before arriving, regardless of vaccination status.
The policy applies to anyone age 6 years and older, and it stipulates that the test must be done at a medical center in the country of origin, with the results submitted at the airport check-in counter.
In other international developments, Taiwan announced that it will end its COVID-19 quarantine for incoming travelers starting on Oct 13, according to Reuters. And Germany-based InflaRx submitted an emergency use authorization application to the US Food and Drug Administration for a first-in-class monoclonal anti-human complement factor antibody treatment.
Sep 29 FIFA World Cup statement
Sep 29 Reuters story
Sep 29 InflaRx statement
