News Scan for Feb 14, 2018

Novel H7N4 avian flu in China
Flu vaccine protection in older adults
Yellow fever fractional dosing

China reports first human infection from novel H7N4 avian flu

China has reported the world's first known novel H7N4 avian flu infection in a human, according to a report today from Hong Kong's Centre for Health Protection (CHP), which based its information on a notification from the mainland's National Health and Family Planning Commission.

The patient is a 68-year-old woman from Jiangsu province whose symptoms began on Dec 25. She was hospitalized on Jan 1 and was discharged on Jan 22. An investigation revealed she had contact with live poultry before she got sick. None of the woman's close contacts had any symptoms during the monitoring period.

A genetic analysis by the Chinese Center for Disease Control and Prevention found that all the H7N4 virus genes were of avian origin, the CHP said. It added that all novel influenza A infections are notifiable diseases in Hong Kong and that, based on seasonal patterns, it expects avian flu activity to be higher in the winter.
Feb 14 CHP statement


Five-season study finds flu VE similar for older, younger adults

Flu vaccination offers similar effectiveness for younger and older adults, but protection was very low for both groups against the problematic H3N2 strain, researchers from the US Centers for Disease Control and Prevention (CDC) and several institutions that are part of a surveillance network team that analyzes flu vaccine effectiveness (VE) reported yesterday in Vaccine.

Reports on flu vaccine protection in older adults have been inconsistent, and to get a better picture, the group looked at effectiveness over five flu seasons—2011-12 through 2015-16—comparing effectiveness in younger adults ages 18 to 49 with that of different age-groups of seniors. Of 20,022 adults seen for acute respiratory infections at the surveillance sites during those five seasons, 24% tested positive for influenza.

VE in those age 65 and older was not significantly lower than that of younger adults against any subtype. Against the 2009 H1N1 virus, VE was 49% and 48%, respectively, and against influenza B, VE was 62% and 55%, respectively. However, against H3N2, protection was low for both groups: 14% (and not statistically significant) for adults age 65 and older and 21% in the younger age-group. The investigators didn't find decreasing VE in adults age 75 and older compared with those 65 to 74.

The researchers didn't find any significant interaction of age and vaccination when they looked at prior vaccination status.

Though they didn't find lower VE in older adults, the team noted that immunogenicity studies have shown lower immune response in that age-group, with some showing waning response and VE over a single season. They said despite lower antibody response, the levels produced may still be enough to provide protection, perhaps along with antibodies from earlier years adding residual protection. The researchers said that improving flu VE for seniors and their younger peers still remains a priority.
Feb 13 Vaccine abstract


Fractional-dose yellow fever vaccine produces good immune response

A fractional dose of yellow fever vaccine, given to address shortages during a 2016 outbreak in the Democratic Republic of Congo (DRC), prompted a good immune response, researchers from the DRC and the CDC reported today in the New England Journal of Medicine.

The outbreak began at the end of 2015, starting in Angola and spreading to neighboring DRC. More than 7,000 suspected cases were reported between the two countries, 962 of them confirmed. The team recruited people from four age-groups at six sites in Kinshasa where the one-fifth-standard dose was given during the immunization campaign, which targeted 7.6 million children age 2 and older and nonpregnant adults.

The researchers measured yellow fever virus neutralizing antibody titers in blood samples obtained before vaccination, comparing them with samples taking at days 28 and 35 after vaccination. Of 716 people who completed follow-up, 98% had an immune response after vaccination. Of 493 who were seronegative at baseline, 98% showed evidence of seroconversion. However, in those who were seropositive at baseline, the percentage who had an immune response after vaccination was lower, at 66%.

The seroconversion was similar to earlier studies that measured the immune response of the full-dose yellow fever vaccine and in earlier clinical trials of the fractional dose that mainly included men. The team said they saw a slightly lower conversion rate in females than males, which has also been observed in clinical trials with the full-dose vaccine.

The authors concluded that the fractional dose is appropriate for response to yellow fever outbreaks and that more studies are needed to see if the method is protective in kids younger than 2, pregnant women, and people with HIV. They added that follow-up testing is under way to gauge protection up to 1 year after vaccination.
Feb 14 N Engl J Med report

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