News Scan for Jul 18, 2017

MERS diagnosis delay
Cholera vaccine efficacy
Flu vaccines and ILI
New Zika assay

MERS diagnosed later in older patients

A study yesterday in the International Journal of Infectious Diseases that measured the time between symptom onset and diagnosis in 537 patients with MERS-CoV in Saudi Arabia found that patients were diagnosed 0 to 36 days after symptoms appeared, with a median of 4 days.

However, patients who are more likely to suffer severe outcomes from MERS-CoV (Middle East respiratory syndrome coronavirus), including the elderly and those with preexisting illnesses, had longer delays in diagnosis than younger and healthier people.

According to the study, the rate of delayed diagnosis was 42% higher in patients older than 65 compared  with patients younger than 30. The authors suggest this may be why older patients are more likely to die from MERS-CoV than younger patients.

Patients with severe symptoms were also diagnosed more than 2 days later than patients who were in stable condition.
Jul 17 Int J Infect Dis study


Review of cholera vaccine studies affirms solid protection for at least 3 years

A meta-analysis of the most recent efficacy estimates for killed oral cholera vaccines suggests that they provide medium to high levels of protection for at least 3 years with the two-dose schedule and can provide similar short-term protection with one dose. A team based at the Johns Hopkins Bloomberg School of Public Health reported its findings yesterday in The Lancet Infectious Diseases.

For their review, the scientists included data from seven randomized, controlled efficacy trials, most with a placebo group, and six observational studies involving lab-confirmed cholera. All of the studies were published since 2010 to provide an updated and more complete picture of the vaccine's protection.

Taken together, the studies showed an average two-dose efficacy of 58% (95% confidence interval [CI], 42% to 69%) and effectiveness of 76% (95% CI, 62% to 85%). Efficacy for children younger than 5 years old was lower than their older counterparts, 30% and 64%, respectively.

The two-dose efficacy estimates were similar for the first 2 years after vaccination, with the level declining to 39% in the third year and 26% in the fourth year. Short-term effectiveness was similar between one- and two-dose regimens.

The researchers said the findings suggest that the one-dose protection findings lend support to using one dose as a practical option for reducing short-term risk in outbreak settings.

In a related commentary, two experts from the Indian Council of Medical Research wrote that the new estimates affirm earlier findings and that the low efficacy in the youngest children continues to influence vaccine policy discussions in endemic countries. They said a better understanding of the reasons for the poor immune response in the age-group are needed, as is the extent of herd protection offered by the vaccines, especially as it affects children.

Cheap, effective oral cholera vaccines offer a viable option for helping to keep cholera at bay, given that water and sanitation improvements can take a long time to implement and the fact that the Vibrio bacteria that cause the disease are known to persist in the environment.
Jul 17 Lancet Infect Dis abstract
Jul 17 Lancet Infect Dis commentary


Study finds limited impact of flu vaccine on flulike illness in seniors

Flu vaccination in older adults reduces the number of infections from flu, but not the number influenza-like illnesses (ILIs), suggesting that other pathogens fill the gap, researchers from the Netherlands reported last week in the Journal of Infectious Diseases.

In a prospective, test-negative, observational study designed to measure the contributions of flu and other respiratory pathogens, the team followed adults age 60 and older over during the 2011-12 and 2012-13 flu seasons, both of which had H3N2 as the dominant strain. They collected nose and throat swabs from sick people and controls to identify viruses and bacteria. They also recorded participants' flu vaccination status.

Influenza was responsible for 18.9% of the ILIs the first season and for 34.2% the following season. Pathogens were detected in 80% of ILI episodes, with influenza, coronaviruses, rhinoviruses, human metapneumovirus, respiratory syncytial virus, parainfluenza virus, and Haemophilus influenzae most common.

Flu vaccination cut the level of infections specifically from flu by 73% (95% CI, 26% to 90%) the first season and 51% (95% CI, 7% to 74%) the second season. The incidence of ILI, however, was similar for both the vaccinated and unvaccinated groups: 7.6% and 4.2%, respectively, the first season and 10.8% and 11.4%, respectively, the second season.

The authors suggested that because other pathogens seem to take up the slack carved out by flu vaccination, there may be a pool of people who are highly susceptible to respiratory infections.

In a related commentary, two Canadian experts wrote that test-negative study designs, which help to ease the healthy vaccinee bias, are helping to tease out the benefits and gaps in flu vaccine protection in older people. They noted that the researchers acknowledged that their study may overestimate the benefit of vaccination, since it involved a relatively healthy population. The commenters noted the importance of factoring in frailty measures and focusing on H3N2 seasons to assess the effectiveness of flu vaccines in older adults.
Jul 13 J Infect Dis abstract
Jul 13 J Infect Dis commentary


New highly sensitive, specific Zika test highlighted

An international research team yesterday described a new diagnostic test for Zika virus that can reliably distinguish it from similar viruses, offering a simple, cost-effective tool for surveillance and clinical management. The group, based at the University of California-Berkeley, reported its findings in Proceedings of the National Academy of Sciences (PNAS).

The antibody test is based on a nonstructural protein 1 (NS1) human monoclonal antibody and was developed by scientists at UC-Berkeley and Humabs BioMed, a private biotechnology company. The work was partly supported by the National Institutes of Health.

The assay was developed from 14 years' worth of patient samples from a collection in Nicaraguan children who had well-documented infections. The collection included longitudinal samples from Zika patients, including those with or without earlier dengue infection and those infected with more than one dengue subtype.

To gauge the sensitivity and specificity of the new assay, the investigators tested a large number of samples from travelers and people with high exposure to Zika and other flaviviruses in five countries. Results showed that the assay was highly sensitive (91.8%) and highly specific (95.9%) for Zika virus.

The assay is based on the ELISA platform, which is widely available throughout the world, and the authors estimated that the cost for reagents and materials is about 25 cents. They also note that the test is a single assay, requiring only one dilution per sample.

Eva Harris, PhD, study coauthor and professor of infectious diseases at UC-Berkeley, said in a statement from the university, "The whole world has been in urgent need of a serological method to distinguish dengue virus from Zika virus infections, and this the first to have such high sensitivity and specificity in dengue-endemic regions."
Jul 17 PNAS abstract
Jul 18 UC-Berkeley press release

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