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Incomplete vaccine inactivation...

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  • Pamela Alley
    Yes, it s equine, but since the RHD/VHD vaccine (at least one anyway, info please?) is formalin-inactivated, I felt this was of interest. PA ... From:
    Message 1 of 1 , Apr 8, 2002
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      Yes, it's equine, but since the RHD/VHD vaccine (at least one anyway, info
      please?) is formalin-inactivated, I felt this was of interest.

      PA
      ----- Original Message -----
      From: ProMED-mail <promed@...>
      To: <promed-ahead@...>
      Sent: Monday, April 08, 2002 8:14 AM
      Subject: PRO/AH> Eastern equine enceph. - USA (California)


      > EASTERN EQUINE ENCEPH. - USA (CALIFORNIA)
      > **********************************************
      > A ProMED-mail post
      > <http://www.promedmail.org>
      > ProMED-mail, a program of the
      > International Society for Infectious Diseases
      > <http://www.isid.org>
      >
      > [see also:
      > Venezuelan equine encephalitis - Honduras 20020320.3775
      > 2001
      > ----
      > Eastern equine enceph., horse - USA (Minnesota) 20010912.2194
      > Eastern equine enceph., horse - USA (Wisconsin) (02) 20010808.1870
      > Eastern equine enceph., horse - USA (Wisconsin) 20010805.1852
      > Eastern equine enceph., horse - USA (Florida) 20010705.1291
      > 2000
      > ---
      > East. equine encephalitis, horses - USA (Virginia) (02) 20000803.1298
      > East. equine encephalitis, horses - USA (Virginia) 20000802.1285
      > Eastern equine encephalitis, human - USA (NC) (02) 20000802.1282
      > Eastern equine encephalitis, human - USA (NC) 20000711.1154
      > East. equine encephalitis, horse - USA (Louisiana) (02) 20000526.0837
      > Eastern equine encephalitis - USA (Louisiana): correction 20000515.0759
      > Eastern equine encephalitis - USA (Louisiana) 20000510.0714
      > Eastern equine encephalitis - USA (Texas): alert 20000420.0575
      > East. equine encephalitis, horse - USA (Louisiana) 20000418.0557
      > 1999
      > ---
      > East. equine encephalitis, horse - USA (Georgia) 19991029.1955]
      >
      > Date: 7 Apr 2002
      > From: Eleanor Kellon <kell@...>
      > Source: CDC [edited]
      > <http://www.cdc.gov/ncidod/EID/vol8no3/01-0199.htm#Figure3>
      >
      >
      > Full results of the investigation into the first recorded case of
      > Eastern Equine Encephalopathy (EEE) in California are now available
      > at the above URL.
      >
      > Although not 100 percent conclusive, the most likely source appears
      > to be incompletely inactivated vaccine virus. The fact that this
      > animal was a yearling (and thus likely being exposed for the first
      > time) is highly significant in light of the relatively low dose of
      > virus involved.
      >
      > The following is a portion of the conclusions:
      >
      > After we excluded disease by natural infection, bioterrorism, and
      > importation, incomplete formalin inactivation of the EEEV (Easter
      > Equine Encephalitis Virus) in the vaccine had to be considered a
      > likely possibility. Previous reports of residual virus in
      > formalin-inactivated vaccines exist.
      >
      > Documented outbreaks due to Poliovirus (PV), Foot-and-mouth disease
      > virus, and VEEV (Venezuelan Equine Encephalopathy Virus) have been
      > directly related to the use of formalin-inactivated vaccines (17-19).
      > Attempts to isolate live EEEV from residual and stored vaccine were
      > unsuccessful. However, this does not eliminate the possibility the
      > horse received live virus with its immunization. If inactivated
      > viruses existed in the vaccine, they were likely present in
      > undetectable levels during vaccine development and testing.
      >
      > Additionally, the live viruses were probably distributed sporadically
      > throughout the vaccine lot, allowing for only an isolated recognized
      > case. The situation could also be analogous to the 1955 "Cutter
      > inactivated poliovirus incident," when children became infected with
      > PVafter vaccination and follow-up investigation disclosed several
      > lots of Salk PV vaccine contained live PV, despite being produced
      > with formalin inactivation in full compliance with federal
      > regulations (19). In the PV vaccine example, live virus was not
      > uniformly distributed in that vaccine lot (20).
      >
      > We further explored the hypothesis of residual live virus in the
      > vaccine through molecular epidemiologic studies. Similar studies were
      > used to examine the role of the VEEV vaccine in the 1967-1972 VEEV
      > pandemic in Central America (21). Unfortunately, the North American
      > variety of EEEV is the most genetically homologous of the
      > alphaviruses and therefore the least conducive to molecular
      > comparison of strains (9,22). In our study, the greatest nucleotide
      > homology in the E1 region was among the horse virus isolate, Vaccine
      > A virus, and the LA50 virus strain.
      >
      > Differences among sequences from Vaccine A EEEV and the horse viral
      > isolate in the E1 region might represent mutations that occurred
      > when virus passed through various hosts (horse brain/BHK cell
      > culture/1) or genetic variants within the vaccine strain. However, we
      > concluded on the basis of the limited number of clones analyzed that
      > there were few to no other EEEV subclones in the horse viral isolate
      > or vaccine virus. The NSP3 region proved to be more highly conserved
      > and therefore less conclusive. Also, very few EEEV sequences that
      > included the nonstructural regions have been published in GenBank, so
      > comparison was limited. Regardless, the Vaccine A EEEV appears to be
      > closely related to the horse viral isolate; thus, the possibility of
      > live virus in the formalin-treated vaccine infecting the horse
      > remains.
      >
      > We are unaware of any reports of problems with this vaccine lot,
      > despite notification of the manufacturer and other state
      > veterinarians. If Vaccine A or portions of the lot contained live
      > virus, many exposed horses may not have been susceptible because of
      > previous immunization or presence of maternal antibodies. In
      > addition, cases may have been unrecognized or unreported. If Vaccine
      > A was the source of infection for this case or other cases, it was
      > probably a rare event.
      >
      > --
      > Eleanor Kellon, VMD
      > Horse Journal
      > <kell@...>
      >
      > [A case of EEE in California is rare. But it is extremely concerning
      > to think this case may be because of the very vaccine used to protect
      > the yearling. - Mod.TG]
      > ......................................tg/pg/lm
      > --
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