Saturday, November 22, 2014

Ebola: Encouraging news but far from victory

The Ebola treatment unit (ETU) in Tubmanburg is the first ETU to be built and staffed by the United States in Liberia / Carol Han, USAID/OFDARecent statistics from West Africa suggest that the epidemic of Ebola virus disease is declining in some areas. While this is welcomed and good news, it's important to remind ourselves that the public health emergency is not over and that significant uncertainties remain. Dr. Joanne Liu, the current president of MSF, described the reasons in an interview with Julia Belluz:
Strictly speaking, when we look at our figures, there is deceleration in the number of cases in a few spots in Liberia and Guinea, but they are still on the rise in Sierra Leone.

There are a few things we need to be conscious about: we have had those decelerations in the past. Basically, it happened while it was spreading in other communities and after that, there was another surge in other hot spots. So we need to make sure it’s an opportunity to consolidate our Ebola isolation centers and case management, strengthen the community information and education. That is key. We need to use this time for that. But the main thing is to not let down our guard.

There’s no room for complacency, no room for mistakes. Every time you go down that path, you pay: you get infected, more people are infected. Ebola does not allow you to make mistakes.
This is certainly true. I think it's also a critical time in another way: With the medical aid in the region and the momentum it is gaining, it would be a shame not to begin asking what will happen when the epidemic is finally conquered. Will the international community simply pull out, leaving a vacuum made more acute by the scores of local healthcare workers lost to Ebola itself? Or, is there a way that the current activity could bolster and influence medicine and public health there for years to come? Some ideas may be creeping into the conversation: US and Liberian officials have decided to reduce the number of Ebola treatment units planned and are discussing spending the money saved on programs aimed at combating future epidemics.

For now, however, we must avoid complacency and remain committed to providing the resources needed to fight the ongoing epidemic. I don't think it's too early to begin conceiving a foundation for improving regional medical and public health capabilities more broadly, however. Perhaps some of the capabilities on site in the affected areas now can be transitioned into a sustainable, effective medical and public health presence at the appropriate time. Not doing so would be a missed opportunity.

(image source: USAID/ Carol Han)

Thursday, November 13, 2014

Influenza vaccine recommendations: Stop needling me!

File:14234CDC Flumist.tifSeasonal influenza is responsible for an estimated 200,000 hospitalizations and 23,000 deaths in the US annually. Each year influenza vaccines are produced based on the viruses forecast to become prevalent. There are two types of vaccine: inactivated influenza vaccine (IIV), delivered via injection, and live attenuated influenza vaccine (LAIV), delivered via a mist sprayed into the nose. Influenza vaccines typically have efficacies exceeding 60% and an estimated 46% of the American public relieves vaccine annually.

While many people are vaccinated each year, it is desirable to increase vaccination rates for at least two reasons. First, vaccine-associated immunity protects individuals from developing potentially serious or fatal disease. Second, high population coverage produces a herd immunity effect: those possessing vaccine-associated immunity cannot become infected and thus cannot infect others. This is especially important for protecting individuals for whom vaccines are contraindicated.

Individuals who are immunocompromised or immunosuppressed are such a group. Consider, for example, patients recovering from hematopoietic stem cell transplantation (HSCT) following myeloablative conditioning. In cases of imperfect donor-recipient match, patients may take immunosuppressive medications as prophylaxis against, or treatment for, graft versus host disease. During this process of immunologic tolerization, which can last months or longer, patients must avoid crowds and limit work/school and social interactions in order to avoid potentially fatal infections. And during this period it is critically important for caregivers and contacts to be vaccinated against influenza and other vaccine-preventable diseases so that they do not become infectious.

LAIV is contraindicated for caregivers of such persons in the Advisory Committee on Immunization Practices (ACIP) guidelines. Because LAIV contains live influenza viruses, a potential exists for transmission of vaccine strain viruses from vaccinees to other persons. The period of viral shedding in vaccinees is variable and relatively short lived. Vaccinated immunocompetent children, for example, shed vaccine viruses for less than 3 weeks, and evidence suggests that shedding may be much shorter lived than that. LAIV-associated shedding occurs in lower titers than is typically observed in disease-associated shedding caused by wild-type influenza viruses.

As several studies have demonstrated higher efficacy of LAIV relative to IIV in children (but see the footnote below), the ACIP has expressed
a preference for the use, when immediately available, of live attenuated influenza vaccine (LAIV) for healthy children aged 2 through 8 years, to be implemented as feasible for the 2014–15 season but not later than the 2015–16 season.
Higher protective efficacy of LAIV in children provides strong rationale for the ACIP statement. Moreover, promoting LAIV as an alternative to IIV in older patient populations may result in increased coverage in those who avoid vaccination due to fear of needles. I wonder if increased use of LAIV might pose additional risk to immunocompromised persons, however, in terms of inadvertent exposure to recent vaccinees shedding live, though attenuated, influenza viruses. Such patients may need to become more meticulous in screening visitors and contacts who may have received LAIV recently.

Footnote: During 2013-2014 there was no measurable effectiveness for LAIV against influenza A (H1N1) among children enrolled in effectiveness studies. The reasons for this are unclear.

(image source: Wikipedia)