News Scan for Feb 24, 2022

News brief

Babies born with Zika at greater risk of dying than those without

Mortality rates among children born with congenital Zika syndrome up to 3 years of age were more than 11 times higher than those without Zika, researchers reported today in the New England Journal of Medicine.

In the retrospective, population-based cohort study, researchers from Brazil and the United Kingdom examined all singleton live births in Brazil from 2015 through 2018, linking live birth records with the Public Health Event Record, which contains information about all recorded suspected cases of microcephaly associated with congenital Zika infection, and the Mortality Information System. They used Cox proportional hazard models to estimate mortality rates and mortality rate ratios for children born with and without Zika.

A total of 11,481,215 children were followed to 36 months of age. By the end of the study period, 398 children live-born children with congenital Zika syndrome and 120,629 children without the syndrome had died. The mortality rate was 52.6 deaths per 1,000 person-years among live-born children with Zika, compared with 5.6 deaths per 1,000 person-years among those without. The mortality rate ratio among live-born children with Zika was 11.3 compared with children without.

Among infants born before 32 weeks of gestation or with a birth weight of less than 1,500 grams, the risks of death were similar among those with and without Zika. Among infants born at term, those with congenital Zika syndrome were 14.3 times as likely to die as those without the syndrome (mortality rate, 38.4 vs 2.7 deaths per 1,000 person-years).

The main causes of death among babies born with Zika, which is transmitted by the Aedes aegypti mosquito, were infectious diseases, diseases of the nervous system, sepsis, and congenital abnormalities, mainly cerebral palsy and microcephaly.

An estimated 1.5 million Brazilians were infected during the country's Zika epidemic, which lasted from April 2015 to November 2016.

"While the overall risk of death remains small, we found babies born with congenital Zika syndrome are at a greater risk of death than those born without," first study author Enny Paixao Crux, PhD, assistant professor at the London School of Hygiene and Tropical Medicine (LHSTM), said in a press release. "This increased risk demonstrates the importance of protecting women, especially those pregnant or of child-bearing age, against the bite of the mosquitoes that carry this virus."
Feb 24 N Engl J Med study
Feb 23 LHSTM press release

Study: Increased flu vaccination could cut flu-linked antibiotics

A study of influenza-associated antibiotic prescribing in California suggests that increasing influenza vaccination coverage could have a modest benefit for reducing antibiotic prescribing, researchers reported today in Epidemiology & Infection.

For the study, researchers from Harvard T.H. Chan School of Public Health and Kaiser Permanente estimated age/diagnosis-specific proportions of antibiotic prescriptions for the Kaiser Permanente Northern California population from 2010 through 2018, looking at prescriptions for all diagnoses, ear infections, and respiratory diagnoses without indication of a bacterial infection.

They estimated antibiotic prescribing associated with influenza, which can lead to bacterial complications such as streptococcal pharyngitis and otitis media (ear infection), by calculating the proportion of all antibiotic prescribing that could be explained statistically by weekly variation in influenza incidence.

The proportion of influenza-associated antibiotic prescribing among all antibiotic prescribing was higher in children aged 5 to 17 years than in children under 5 years old, ranging from 1.4% in children younger than 1 year to 2.7% in children ages 15 to 17 years.

For adults over 20 years of age, the proportion of influenza-associated prescribing among all prescribing was lower, ranging from 0.7% for ages 25 to 29 to 1.6% for ages 60 to 64. Most influenza-associated prescribing in children under 10 was for ear infections, while for age-groups over 25, 45% to 84% of influenza-associated antibiotic prescribing was for respiratory diagnoses without a bacterial infection.

"Our results suggest an overall modest benefit of increasing influenza vaccination coverage for reducing antibiotic prescribing, with that benefit being greatest for school-age children, as well as the benefit of reducing unnecessary antibiotic prescribing for respiratory diagnoses with no bacterial indication in persons aged over 25y, both of which may further contribute to the mitigation of antimicrobial resistance," the study authors write.
Feb 24 Epidemiol Infect abstract

High-path avian flu hits Michigan flock; more wild bird cases in 3 states

Michigan's Department of Agriculture and Rural Development (MDARD) today announced a highly pathogenic avian flu outbreak in a noncommercial backyard flock, the seventh state to report the virus in poultry. Also, the US Department of Agriculture (USDA) reported five more high-path H5 detections in wild birds in three states: Florida, Kentucky, and North Carolina.

In a statement, MDARD said the outbreak occurred in Kalamazoo County, located in the southwestern part of the state. The birds were tested after several birds from the flock died and others showed symptoms. The site is under quarantine, and the birds have been depopulated.

The USDA's Animal and Plant Health Inspection Service (APHIS) said the samples were tested at the Michigan State University Veterinary Diagnostic Laboratory and at the APHIS National Veterinary Services Laboratory in Ames, Iowa.

The 5 new highly pathogenic H5 detections in wild birds all involve those found dead that underwent testing and bring the total number of recent detections to 252. The latest spate of listings include the first two from Kentucky, which has already reported the virus at a broiler farm in Webster County. The wild birds that tested positive from the state are two snow geese from Ballard County, in the southwest corner.

The other new detections include two black vultures at a zoo in Florida's Brevard County, which follow two early February detections in Palm Beach County waterfowl. Also, North Carolina reported the virus in a wild duck in Carteret County, the fourth county in the state to report the virus.

The US Centers for Disease Control and Prevention (CDC) yesterday posted a new situation summary of the evolving global and domestic situations with highly pathogenic H5 in poultry and wild birds, noting that the risk to humans is still low, despite the latest US detections, though some groups such as poultry workers may face more exposure to the virus.
Feb 24 MDARD statement
Feb 24 APHIS statement
APHIS wild bird avian flu page
CDC avian flu situation summary

ACIP recommends tickborne encephalitis and cholera vaccine for some

The vaccine advisory group to the CDC yesterday recommended that certain groups receive a recently approved vaccine against tickborne encephalitis (TBE) and that children traveling to cholera outbreak areas receive the cholera vaccine, according to Healio, a medical news website.

The TBE vaccine recommendation from the CDC's Advisory Committee on Immunization Practices (ACIP) involves a vaccine called Ticovac from Pfizer, which was approved by the Food and Drug Administration in August 2021. The vaccine is the first of its kind and is indicated for people ages 1 and older who are visiting or living in TBE-endemic areas.

In its vote yesterday, ACIP recommended the TBE vaccine for lab workers who are potentially exposed to the virus and people moving to or visiting endemic areas.

ACIP recommended the cholera vaccine for children ages 2 to 17 years who are traveling to areas experiencing active cholera transmission. In 2017, the CDC finalized a similar ACIP recommendation for adults ages 18 to 64.

The CDC typically accepts ACIP recommendations.
Feb 23 Healio story
Aug 13, 2021, Pfizer statement

COVID-19 Scan for Feb 24, 2022

News brief

High immunity, low vaccine rate in South Africa point to prior infections

A seroepidemiologic survey of 7,010 people in Gauteng province, South Africa, before the SARS-CoV-2 Omicron variant outcompeted the Delta strain shows that 80% of those older than 50 years had antibodies against the virus, with most seropositivity likely generated by previous infection.

In the study, published yesterday in the New England Journal of Medicine (NEJM), South African researchers analyzed dried-blood samples from participants from 3,047 households from Oct 22 to Dec 9, 2021. They looked for anti–SARS-CoV-2 immunoglobulin G (IgG) antibodies and assessed COVID-19 cases, hospitalizations, and deaths and excess deaths through Jan 12, 2022. Omicron was first identified in the region on Nov 25, 2021, but didn't become dominant until December.

Of the 7,010 participants, 18.8% had been vaccinated against COVID-19. IgG seroprevalence ranged from 56.2% (95% confidence interval [CI], 52.6% to 59.7%) among children younger than 12 years to 79.7% (95% CI, 77.6% to 81.5%) in adults older than 50. Vaccinated participants had higher rates of IgG seropositivity than their unvaccinated peers (93.1% vs 68.4%).

A study of many of the same participants in January 2021 had found that 19.1% of the population had anti–SARS-CoV-2 IgG.

According to epidemiologic data, COVID-19 cases rose and then declined faster during the study period than in previous surges, and cases were milder as well, with lower rates of hospitalization, death, and excess death.

"We think that the decoupling of the incidence of Covid-19 cases from the incidences of hospitalization and death during the omicron-dominant wave in South Africa heralds a turning point in the Covid-19 pandemic, if the primary goal is protection against severe disease and death rather than prevention of infection," the authors concluded.

In an audio interview, NEJM Editor-in-Chief Eric Rubin, MD, PhD, noted that 40% of samples had antibodies against the nucleocapsid protein expressed by the virus, while 70% had antibodies against the virus's spike protein generated by vaccines. With only a third of the population vaccinated against COVID-19, the finding suggests that nucleocapsid antibody isn't a very sensitive marker for previous infection, he said, but using both types of antibodies may be.

"Thus, in this part of South Africa, immunity levels were very high, even though vaccination rates were low, suggesting that there had been a considerable amount of infection during earlier outbreaks."
Feb 23 NEJM study and audio interview

Study: Innova COVID-19 rapid test may miss many asymptomatic cases

The Innova lateral-flow (rapid antigen) test (LFT) may miss 20% of COVID-19 infections at UK testing centers, 29% of asymptomatic cases at mass-testing centers, and 81% of asymptomatic infections at university screenings, predicts an analysis published yesterday in BMJ. Innova tests are not sold in the United States.

A team led by University of Birmingham in England led the study, which used linked empirical data on the accuracy of the test and the probability of a positive viral culture or viral transmission, as well as viral loads in COVID-19 patients in the three settings.

Estimated sensitivity of the Innova test was based on 70 COVID-19 patients, while infectiousness was based on viral cultures of 246 respiratory samples from 176 patients and 2,474,066 close contacts. Viral loads were based on 70 infected patients in Liverpool and 62 in Birmingham.

The researchers predicted that the test would miss 20% of people tested at a National Health Service Test-and-Trace center, 29% of asymptomatic patients at a municipal mass testing site, and 81% asymptomatic attendees at a university screening. The test, they found, would also miss 38%, 47%, and 90% of sources of secondary infections, respectively.

In contrast, two mathematical models underestimated missed infections at 8%, 10%, and 32% in each of the three settings, respectively, while the assumptions from another model estimated that none would be missed.

The researchers said that the percentage of missed infections is large enough to have clinical implications. "The proportion missed varied between settings because of different viral load distributions and is likely to be highest in those without symptoms," they wrote. "Key models have substantially overestimated the sensitivity of LFTs compared with empirical data."

In a related commentary, Angela Raffle, MBChB, of the University of Bristol, and Mike Gill, MBBS, a former regional director of public health, said that the lack of hard evidence of the utility of lateral flow tests has been striking in light of the more than £7 billion ($9.4 billion US) Britain has spent on these tests.

"The clear implication is that any positive impact from the detection of asymptomatic people may be outweighed by the effects of infectious people being falsely reassured and therefore mixing with others, perhaps even ignoring their symptoms," they wrote. "Unsurprisingly, testing is therefore chaotic and wasteful."
Feb 23 BMJ study and commentary