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2011 December 31

Prevnar 13 approved for adults

The FDA recently approved the Prevnar 13 vaccine against Streptococcus pneumoniae for adults.  Previously, only the Pneumovax 23 vaccine was approved for adult use.  I’m asplenic, since I had my spleen removed after a bike crash in 2000, and so am in a high-risk class for pneumonia caused by S. pneumoniae.  I’ve already had vaccination with Pneumovax 23, so is there any point to getting Prevnar 13 as well?

First, let’s look at the serotypes covered (the 13 and 23 of the names). According to reference.medscape.com’s article on Prevnar 13, it protects against “invasive disease caused by S pneumoniae serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F.” According to the manufacturer Merck’s page about the serotypes, Pneumovax 23 is for “prevention of pneumococcal disease caused by the 23 serotypes contained in the vaccine  (1, 2, 3, 4, 5, 6B, 7F, 8, 9N, 9V, 10A, 11A, 12F, 14, 15B, 17F, 18C, 19F, 19A, 20, 22F, 23F, and 33F).”

It looks like I’m covered for all the serotypes in Prevnar 13 except 6A.  The remaining questions are

  • whether Prevnar 13 provides better protection against the serotypes it covers,
  • whether the two vaccines raise different sorts of antibodies (causing increased protection if combined), and
  • whether serotype 6A is common enough in adults to pose a risk to me.

Prevnar 13 did produce larger effects than Pneumovax 23 for the strains they have in common, so it probably does confer some extra protection. [Vaccines and Related Biological Products Advisory Committee November 16, 2011 FDA Briefing Document]  Also, doing Prevnar 13 followed a few years later by Pneumovax 23 had stronger effects than Pneumovax 23 alone, so they do seem to combine.  In one study that compared Pneumovax 23 and Prevnar 13, in patients who had had Pneumovax 23 at least 5 years earlier, Prevnar 13 showed 1 to 3 times as much effect on the serotypes in common, and 9.6 times as much effect on serotype 6A.

Experiments have been done to see whether Pneumovax 23 is protective against serotype 6A.  For example, Lee et al. The effect of age on the response to the pneumococcal polysaccharide vaccine BMC Infectious Diseases 2010, 10:60 showed Pneumovax 23 working about as well against 6A as against the serotypes 4 and 19A, which are included in the vaccine.  The assumption has been that including 6B provided enough cross-reaction that 6A was also covered.  This seems to be reasonably true, at least for adults, and so the inclusion of 6A in Prevnar 13 would not be sufficient reason to get the vaccine, given that I’ve had Pneumovax 23 fairly recently.

But I’ve already had 2 doses of Pneumovax 23 and “because data are not sufficient concerning the safety of 23vPS when administered ≥ 3 times, revaccination after a 2nd dose is not routinely recommended,” so the next time I get a pneumococcal vaccine it should probably be Prevnar 13.  There does not seem to be any urgent need to do so, and I should probably wait for another decade or so, and then get Prevnar 13 (or whatever has replaced it by then) to bring my immune defenses back up.

 

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