POST 01058E : ORAL POLIO VACCINE COLOUR

POST 01058E : ORAL POLIO VACCINE COLOUR Follow-up on Post 01050E 25 February 2007 _______________________________ Hans Everts (mailto:[email protected]) from WHO replies to Jedeth Mamora's question on OPV colour. _______________________________ As a response to the message from Jedeth Mamora in Indonesia first a small but important correction. The VVM does not measure effectiveness of the vaccine, but heat exposure. That is not just a matter of semantics. A clearly polluted vial with a good VVM should not be used. Heat exposure is only one of several components that contribute to the loss of potency. The issue of coloured OPV was submitted to a technical colleague, Jackie Fournier-Caruana, here at WHO some time ago. Her response was the following: The pink color of OPV (either tOPV or mOPV) is given by the presence of phenol red used as pH indicator. This reagent is a residual product from the vaccine production on cells but can also be added at the time of the formulation. Its pH range is from 6.4 to 8 and its color varies from yellow at pH 6.4 to red at pH 8. In the past, WHO received similar complaints from the fields for tOPV produced by different manufacturers and more often for vaccine presented in plastic dispenser than in glass vial. Further to investigation conducted at that time in conjunction with manufacturers, it was concluded that the slight variation of pH leading to the change of colour could be due to exposure to evaporating dry ice and production of CO2. However, the potency and efficacy of the vaccine are not affected by this change of pH, provided that the range of 6.5-7.2 be respected, corresponding to a color varying from yellow to pink red. Similar observations were made by Mauler and Gruschkau who studied monovalent polio vaccines with pH values ranging from 5.5 to 8.0. They concluded that polio vaccines were remarkably stable within the pH range 6.5-7.2. Reference to their original article (Mauler R, Gruschkau H. : "On stability of oral poliovirus vaccines". Developments in biological standardization, 1978, 41: 267-270) was included in the document "Thermostability of vaccines (WHO/GPV/98.07. )" . But this article is no longer available and the WHO document has now been replaced by a revised version "Temperature sensitivity of vaccines (WHO/IVB/06.10)" in which the reference does not appear anymore. The conclusion is that the change of the colour does not invalidate the VVM reading. ______________________________________________________________________________ All members of the TechNet21 e-Forum are invited to send comments on any posting or to use the forum to raise a new discussion or request technical information in relation to immunization services. The comments made in this forum are the sole responsibility of the writers and do not in any way mean that they are endorsed by any of the organizations and agencies to which the authors may belong. ______________________________________________________________________________ Visit the TECHNET21 Website at http://www.technet21.org You will find instructions to subscribe, a direct access to archives, links to reference documents and other features. ______________________________________________________________________________ To UNSUBSCRIBE, send a message to : mailto:[email protected] Leave the subject area BLANK In the message body, write unsubscribe TECHNET21E ______________________________________________________________________________ The World Health Organization and UNICEF support TechNet21. The TechNet21 e-Forum is a communication/information tool for generation of ideas on how to improve immunization services. It is moderated by Claude Letarte and is hosted in cooperation with the Centre de coopération internationale en santé et développement, Québec, Canada (http://www.ccisd.org) ______________________________________________________________________________