Mike the Mad Biologist

In the midst of all of the discussion about improving healthcare, one issue that has been neglected is the role of poverty in poor healthcare outcomes. One group that is hit particularly hard is the homeless. The Toronto Invasive Bacterial Diseases Network reports that the homeless are thirty times more likely to be diagnosed with pneumonia caused by Streptococcus pneumoniae than the population at large:

We identified 69 cases of invasive pneumococcal disease and 27 cases of laboratory confirmed pneumococcal pneumonia in an estimated population of 5050 homeless adults. The incidence of invasive pneumococcal disease in homeless adults was 273 infections per 100,000 persons per year, compared to 9 per 100,000 persons per year in the general adult population. Homeless persons with invasive pneumococcal disease were younger than other adults (median age 46 years vs 67 years, P<.001), and more likely than other adults to be smokers (95% vs. 31%, P<.001), to abuse alcohol (62% vs 15%, P<.001), and to use intravenous drugs (42% vs 4%, P<.001). Relative to age matched controls, they were more likely to have underlying lung disease (12/69, 17% vs 17/272, 6%, P = .006), but not more likely to be HIV infected (17/69, 25% vs 58/282, 21%, P = .73). The proportion of patients with recurrent disease was five fold higher for homeless than other adults (7/58, 12% vs. 24/943, 2.5%, P<.001). In homeless adults, 28 (32%) of pneumococcal isolates were of serotypes included in the 7-valent conjugate vaccine, 42 (48%) of serotypes included in the 13-valent conjugate vaccine, and 72 (83%) of serotypes included in the 23-valent polysaccharide vaccine. Although no outbreaks of disease were identified in shelters, there was evidence of clustering of serotypes suggestive of transmission of pathogenic strains within the homeless population.

When you consider that the typical non-homeless pneumococcal infection is in an older or elderly person, while these infections in the homeless are not, and yet the homeless are still at thirty-fold risk of infection compared to an middle-aged to elderly population, it becomes apparent how debilitating homelessness is.

One relatively straightforward way to combat this problem is through use of the PCV7 (pneumococcal) vaccine, since once you’re vaccinated, you’re protected against the S. pneumoniae strains used to make the vaccine (which, in the homeless, are >85% of cases):

…it is clear that the very high rates of invasive pneumococcal disease, the limitations of current pneumococcal vaccines, and the challenges of pneumococcal vaccination program delivery in homeless populations mean that the coordination of many different programs will be necessary to effectively reduce the burden of pneumococcal disease in this population. The provision of permanent housing and improved living conditions in crowded shelters might be expected to reduce transmission of this pathogen. Prevention and treatment programs for alcohol, smoking and substance abuse, and programs to improve HIV diagnosis and care delivery might prevent a fraction of cases; similarly, increasing influenza vaccination rates might be effective in preventing those cases secondary to influenza…. While all of these programs may be necessary – and all with have benefits beyond pneumococcal disease – they are also relatively expensive and difficult to implement. Thus, studies of the effect of systematic or targeted pneumococcal vaccination programs against S. pneumoniae in homeless populations, and the development of more effective pneumococcal vaccines for adults are both urgently needed.

It is tragic that the pneumococcal vaccine is so underutilized for two at-risk groups: the homeless and the elderly. As I’ve stated before, while vaccination should not be mandatory, we–and as this study shows, we is not limited to the U.S.–need to be far aggressive in using vaccines to combat infectious disease. Any time a group is thirty-fold more likely to contract disease than a population with a median age of 67, that is a healthcare care crisis.

Cited article: Plevneshi A, Svoboda T, Armstrong I, Tyrrell GJ, Miranda A, et al. 2009 Population-Based Surveillance for Invasive Pneumococcal Disease in Homeless Adults in Toronto. PLoS ONE 4(9): e7255. doi:10.1371/journal.pone.0007255

Comments

  1. #1 "GrrlScientist"
    October 8, 2009

    homelessness and poverty in the USA is something close to a major crime with a life sentence, although no one would state in quite that way. americans don’t care about the homeless unless one happens to sit next to them on the subway. even mayor mike bloomberg — one of the richest men in america — is charging the homeless for the privilege of staying in a public shelter! in general, from what i’ve seen, americans would be quite happy if all the homeless just curled up in a dumpster and died, so developing a public health strategy to be ” aggressive in using vaccines to combat infectious disease” among the homeless and poor is never going to happen in this country where money is both god and king.

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