News Scan for May 20, 2016

Yellow fever in Angola
;
US flu activity drops
;
Smallpox vaccine order
;
Bivalent polio vaccine

Yellow fever outbreak in Angola slows, but WHO still worried

Only a few new yellow fever cases have been reported in Angola in the past week, but the mostly urban epidemic is still a big concern because of persistent transmission in seven provinces and expansion to new ones, the World Health Organization (WHO) said in its weekly update today.

The report comes a day after a WHO emergency committee said the outbreak is a serious problem but does not constitute an official public health emergency of international concern.

The agency didn't specify the number of new cases in the past week, but a graph indicates it may be fewer than 10. The cumulative count has reached 2,420 suspected cases and 298 deaths, with another 55 cases exported to three other countries.

Of the 2,420 cases reported in Angola, 736 have been laboratory-confirmed, the WHO said. "Despite vaccination campaigns in Luanda, Huambo and Benguela provinces, circulation of the virus in some districts persists," the report added. Fourteen of the 18 provinces have confirmed cases, and suspected cases have been reported in all provinces.

The Democratic Republic of the Congo (DRC) has reported 42 yellow fever cases imported from Angola, while Kenya has reported 2 imported cases and China 11, the WHO said. Two other cases in the DRC have been classified as locally acquired.

Uganda, meanwhile, had 60 yellow fever cases as of yesterday, including 7 confirmed ones, but genetic tests indicate they are not linked to Angola, the WHO said.

The agency reiterated that the outbreak in Angola and DRC is concentrated in major cities and poses a serious risk of spread to other provinces, with transmission persisting in Luanda province despite the vaccination of 7 million people. The WHO is also worried that the outbreak may spill over to other neighboring countries, such as Namibia and Zambia, where the yellow fever risk is normally considered low and the populations are not vaccinated.
May 20 WHO update
May 19 CIDRAP News story

 

Retreat of US seasonal flu cases speeds up

Seasonal influenza activity across the United States faded more rapidly last week, leaving no states reporting high or even moderate influenza-like illness (ILI) counts, the Centers for Disease Control and Prevention (CDC) said in its weekly update today.

Only one CDC region, comprising most of the Southeast, had ILI activity above its specific baseline, the CDC said. The only jurisdiction with moderate activity was Puerto Rico, which has been reporting high ILI counts for months.

ILI cases accounted for just 1.4% of visits to sentinel clinics around the country, down from 1.8% a week earlier and well below the national baseline of 2.1%.

Flu cases remained geographically widespread in two states (New York and Delaware) and Puerto Rico, compared with three states and Puerto Rico the week before, the CDC reported.

One flu-related pediatric death was reported last week, raising the seasonal total to 68. The death involved an influenza B virus and occurred in early April.

The share of overall deaths attributed to pneumonia and flu in the CDC's 122 Cities Mortality Reporting system held steady at 6.7%, which is the same as the epidemic threshold for the week.

As the percentage of respiratory samples testing positive for flu dropped further, the proportion of type B viruses continued to rise, which is not unusual near the end of the flu season. The CDC said 7.1% of 10,510 samples were positive, down from 8.2% of 11,153 samples the previous week. Type B viruses made up 72.3% of isolates that were typed.

As for flu-related hospitalizations, the cumulative count for the season reached 31.3 cases per 100,000 population, compared with 31.0 the week before.
May 20 CDC FluView update

 

BARDA orders $100 million supply of smallpox vaccine

Biotechnology company Bavarian Nordic announced yesterday that it had received a $100 million order for bulk Imvamune from the US Biomedical Advanced Research and Development Authority (BARDA).

Imvamune is a non-replicating smallpox vaccine intended for use in people with contraindications to replicating vaccine, including people with atopic dermatitis and HIV, the company said.

BARDA's most recent order will be manufactured in 2017. The Imvamune doses are intended to be converted into a freeze-dried formulation once the process has been commercially approved in the United States. Freeze-dried, non-replicating smallpox vaccine has a longer shelf life than the liquid-frozen doses currently maintained in the US Strategic National Stockpile.

The US government has now spent a total of $233 million on bulk Imvamune since 2015. Dose prices will be determined once the contract for delivering the vaccine is finalized, a spokesperson for Bavarian Nordic said.

"It has been investments like this by BARDA, and the research at the NIH [National Institutes of Health], which have allowed successful medical countermeasures to be stockpiled," said Paul Chaplin, PhD, Bavarian Nordic President and Chief Executive Officer.
Mar 19 Bavarian Nordic press release

 

Study: Combined bOPV and IPV offers protection against type 2 poliovirus

Bivalent types 1 and 3 oral poliovirus vaccine (bOPV) induces immunity to poliovirus serotypes 1 and 3, and the addition of inactivated poliovirus vaccine (IPV) prompts serocoversion to poliovirus type 2 (PV2) in infants, according to a study yesterday in The Lancet.

Trivalent oral poliovirus vaccine (tOPV) was withdrawn from global polio immunization schedules in April, raising questions about whether infants receiving bOPV would be protected against PV2. Researchers from the Latin American IPV001BMG Study Group assessed the effectiveness of bOPV and bOPV plus one or two doses of IPV compared with tOPV in a total of 939 infants in Colombia, Dominican Republic, Guatemala, and Panama.

Almost all infants who received three doses of either bOPV or tOPV (97.7%) seroconverted to poliovirus types 1 and 3. Among 198 infants who received only bOPV, 19 seroconverted (ie, developed neutralizing antibodies) to PV2 at 18 weeks, an effect likely attributable to prior community exposure, the authors said.

Most infants given one dose of IPV with bOPV (156 of 194, or 80.4%) seroconverted to PV2 at 18 weeks, and twenty additional infants in this group seroconverted after being challenged with a monovalent type 2 oral poliovirus vaccine (mOPV2). All infants receiving two doses of IPV with bOPV (193 of 193) seroconverted at 40 weeks.

Fecal viral shedding of PV2 occurred in 72.5% to 78.1% of all infants who received bOPV 1 week after the mOPV2 challenge. Infants who received one or two doses of IPV experienced a small but significant decrease in titers and duration of shed virus, the authors said.

Given bOPV's ability to promote high rates of immunity against poliovirus types 1 and 3, and seroconversion to PV2 after dosing with IPV, the authors support global withdrawal of the trivalent vaccine.

In a related commentary yesterday in The Lancet, Edward P. K. Parker, MSc, and Nicholas C. Grassly, PhD, both of Imperial College London, cautioned that seroconversion results may not always mean that infants are protected against disease.

High PV2 shedding rates in infants who received bOPV and an MOPV2 challenge are concerning, the authors said, noting that bOPV will not stop the spread of type 2 circulating vaccine-derived poliovirus in regions with poor sanitation. Though the authors also support the tOPV withdrawal, they add, "We must also be ready to respond rapidly with mOPV2 should an outbreak occur."
May 19 Lancet study
May 19 Lancet
commentary

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