• In its weekly update today, the Centers for Disease Control and Prevention said US flu activity remains low in most of the country, with most markers, including hospitalizations and deaths, continuing to drop for the week ending Feb 18. The percentage of outpatient visits for flu, at 2.6% last week, remained just above the national baseline of 2.5%. The percentage of influenza B samples rose slightly, from 10.4% to 13.3%. Four more pediatric flu deaths were reported, raising the season's total to 115.
• Interim estimates of flu vaccine effectiveness in the US flu season, based on two ongoing studies at the Marshfield Clinic in Wisconsin, suggest that the vaccine was 54% effective for preventing medically attended influenza A infection in people younger then 65 years and was 71% in children and adolescents, according to a report published today in  Morbidity and Mortality Weekly Report. Flu vaccines help cut infections, complications, and deaths, but protection is suboptimal, averaging 10% to 60% from 2004 to 2018, according to CDC data, a factor driving an international push for more effective flu vaccines. Effectiveness is known to vary by season, flu virus subtype, and antigenic match with circulating strains.

• The World Health Organization flu vaccine strain selection committee today announced its recommendations for the Northern Hemisphere's upcoming (2023-24) flu season, keeping most of the strains the same as for the current season. The only difference is a change in the 2009 H1N1 strain for both egg and cell/recombinant versions, swapping earlier virus strains with 2022 versions. The H1N1 strain selections for the Northern Hemisphere are different than the ones included in the vaccine for Southern Hemisphere's 2023 flu season.

Surges in COVID-19 cases in the United States were associated with increased outpatient antibiotic prescribing in adults in 2020, according to an ecological analysis published this week in Open Forum Infectious Diseases.

For the study, researchers with One Health Trust and Johns Hopkins University analyzed data on systemic antibiotic prescriptions collected from retail pharmacies from 2017 through 2020, along with county-level COVID-19 case data for 2020 and data on non-pharmaceutical interventions (NPIs) such as masking that might have reduced transmission of other upper respiratory infections. Their aim was to estimate the relative importance of COVID-19 cases, NPIs, and sociodemographic factors in driving antibiotic prescribing during the first year of the pandemic.

Total antibiotic prescriptions fell by 26.8% from March 2020 to December 2020 compared with 2017 through 2019, likely because of reduced healthcare-seeking behavior. But each 1% increase in monthly county-level COVID-19 cases was associated with a 0.009% increase in monthly antibiotic prescriptions per 100,000 population dispensed to all ages—the equivalent of 1,000 antibiotic prescriptions for every 1% increase in COVID-19 cases nationally.

In a sub-analysis with children, a 1% increase in monthly COVID-19 cases was associated with a 0.12% decrease in the number of monthly antibiotic prescriptions.

Antibiotic use may have continued even when infections were likely viral.

NPIs did not have an impact on all-ages prescribing, but counties with schools open for in-person instruction were associated with a 0.044% increase in monthly prescriptions per 100,000 children compared with counties that closed schools. Movement restriction and face mask requirements were associated with lower prescribing among children.

The authors conclude that since other studies have found that bacterial co-infection in COVID-19 patients is rare, and that antibiotics were overused for COVID-19 in the first year of the pandemic, at least a fraction of the increased antibiotic prescribing they found may have been inappropriate.

"The evidence here suggests that antibiotic use may have continued even when infections were likely viral," they wrote. "Further research is needed to understand why clinicians continue to prescribe antibiotics in these situations and how to modify this behavior."

Two years into the COVID-19 pandemic, US cancer screening rates still hadn't recovered to pre-crisis levels, putting millions at risk for missed diagnoses, according to a study published yesterday in the Journal of Clinical Oncology.

American Cancer Society (ACS) researchers used data from the 2019 and 2021 National Health Interview Survey to estimate the number of US Preventive Services Task Force (USPSTF)-recommended breast, cervical, prostate, and colorectal cancer screenings performed after the pandemic began.

The USPSTF recommends screening for breast cancer for women aged 50 to 74 years, cervical cancer for women aged 21 to 65 who have not had a hysterectomy, prostate cancer for men aged 55 to 69, and colorectal cancer for men and women aged 50 to 75.

Fewer breast, cervical, prostate screenings

From 2019 to 2021, past-year screenings declined from 59.9% to 57.1% for breast cancer, from 45.3% to 39.0% for cervical cancer, and from 39.5% to 36.3% for prostate cancer. Asian adults saw the biggest declines, ranging from -25% for breast cancer to -50% for prostate cancer.

The percentages translate to missed screenings for roughly 1.1 million women for breast cancer, 4.4 million women for cervical cancer, and 700,000 men for prostate cancer.

Colorectal cancer screening didn't change, because past-year at-home stool testing increased from 7.0% to 10.3%, offsetting the drop in colonoscopy from 15.5% to 13.8%. Although about 1.3 million fewer adults received a colonoscopy, 3.6 million completed stool testing, for a net gain of 1.5 million. Increases in stool testing were most pronounced among Black (66%) and Hispanic (82%) adults and those with low socioeconomic status (52%).

It's critical to get people back into their doctor’s offices to help prevent and catch cancer at its earliest stages.

The authors said that the increases in at-home stool testing among Black and Hispanic patients may have helped reduce racial and socioeconomic disparities in colorectal cancer screening, although positive tests still require follow-up colonoscopy.

"It's critical to get people back into their doctor’s offices to help prevent and catch cancer at its earliest stages when it might be easiest to treat," lead author Jessica Star, MA, MPH, said in an ACS news release.

In its weekly review of COVID-19 data today, the Centers for Disease Control and Prevention (CDC) said indicators continue to decline, with the 7-day average for new daily cases 33,722, down 9.2% from a week ago.

New deaths from the virus are averaging 344 a day, down 15.2% compared to the previous week. Likewise, new daily hospitalizations are down 4.9% compared to the previous week's average.

The CDC noted that it will switch to an every-other-week schedule for its updates starting on Mar 3.

Also today, the CDC released new Omicron variant projections, showing a continued increase in XBB.1.5 viruses, which are now at 85%, up from nearly 80% the previous week. The CDC said XBB.1.5 is growing in all US regions, and other lineages show very slow or no growth.

In in other COVID developments, Pfizer and BioNTech today announced that it has submitted an application to the Food and Drug Administration (FDA) for full licensure of its bivalent COVID-19 vaccine for use in people ages 12 and older for primary and booster doses.

Four countries reported vaccine-derived polio cases this week, according to the latest update from the Global Polio Eradication Initiative (GPEI).

The Democratic Republic of the Congo reported four cases of circulating vaccine-derived poliovirus type 2 (cVDPV2) in Haut Lomami province, bringing the number of 2022 cases to 287. Yemen reported 1 cVDPV2 case in Alhudaidah, bringing its 2022 total to 161 cases, along with five cVDPV2-positive environmental samples—two in Alhudaidah and three in Aden.

Mozambique reported two cVDPV type 1 cases in Zambezia, after recording 21 cases in 2022. Madagascar reported one cVDPV1 case in Sava and eight cVDPV1-positive environmental samples in Analamanga. The country has reported 14 cVDPV1 cases for 2022.

Vaccination efforts

In other polio news, GPEI said approximately 585 million doses of the novel oral polio vaccine type 2 (nOPV2) have been administered to date under the World Health Organization's Emergency Use Listing procedure.

The vaccine is a modified version of the type 2 monovalent OPV that has been shown in clinical trials to provide comparable protection while being more genetically stable and less likely to be associated with the emergence of cVDPV2 in low-immunity settings.