Il ceppo Urabe AM-9 della parotite è stato per molti anni contenuto nei vaccini trivalenti.

Da molti studi epidemiologici in Canada, Inghilterra e Giappone è stato visto che questo ceppo causava numerose encefaliti 

iN gIAPPONE NEL 1989 sI PASSO DA 1 A 7 CASI SI MENINGITE OGNI MILLE VACCINATI, UN NUMERO MOLTO ALTO

TUTTO CAUSATO DAL CEPPO PER LA PAROTITE Urabe AM-9 CHE FU TOLTO DAI VACCINI TRIVALENTI E SOSTITUITO CON IL CEPPO MAGGIORMENTE SICURO MA CON MINOR EFFICACIA E CIOE'

MUMPSVAX® (Mumps Virus Vaccine Live), the Jeryl Lynn™ (B level) strain of mumps virus propagated in chick embryo cell culture

MMR Vaccines

The MMR vaccines were introduced in October 1988, as part of a campaign to reduce childhood illness. They are a triple vaccine, using the mumps, measles and rubella live viruses.

Problems with MMR vaccines

Until September 14 1992 there were three types of MMR vaccine available:

Pluserix-MMR and Immravax vaccines contain the Urabe strain of mumps vaccine virus; MMRII vaccine contains the Jeryl Lynn strain of mumps vaccine virus.

On 14 September 1992 the Chief Medical Officer announced that there were to be "Changes in the supply of vaccine". From that date onwards, only MMRII would be available. The following is an extract from his letter giving the reasons for withdrawal:

"This change in vaccine supply arrangements has been considered prudent following reports of generally mild transient meningitis caused by the mumps vaccine virus in some children who recently received the Urabe mumps vaccine containing products, Pluserix-MMR or Immravax. The rate of post-immunisation meningitis following Jeryl Lynn mumps vaccine (which MMRII contains) is much lower.

Incidence of mumps virus meningitis:

"Meningitis after natural mumps has been reported to occur at a rate of approximately 1 per 400 cases.”

"Studies recently undertaken in one Public Health Laboratory, and supported by similar studies in several other Public Health Laboratories, suggest that the incidence of virus positive post-immunisation meningitis from the Urabe strain of mumps vaccine virus may be approximately 1 in 11,000[16] immunised children. This rate of vaccine-associated meningitis is appreciable (sic) lower than that reported after natural mumps infection”

.

"Vaccine-associated meningitis occurs around three weeks after immunisation generally. In those instances reported so far it appears to be a milder and more transient illness than meningitis from wild virus. This is what one might expect with an attenuated virus. The risk benefit ratio therefore remains strongly in favour of the immunisation of all children with any MMR vaccine. However the MMRII vaccine is preferred where this is available because of the much lower risk of vaccine associated meningitis."[17]

Even though the Chief Medical Officer mentioned only "changes in supply", both Immravax and Pluserix have subsequently been withdrawn altogether.[18]

We are troubled that there seems to be a certain amount of massaging of the figures. In the passage just quoted, side effects of one in 11,000 are mentioned. Later, it will be seen that they were brought down to 1/4000[19]. But even that is not the end of the story as this extract from a Japanese study about the safety of MMR vaccines (with the Urabe mumps strain) will show:

"During the 8‑month period extending from April to October, 1989, in Gunma Prefecture, 11 750 children received MMR vaccination according to information supplied by the prefectural public health center.  The incidence of MMR meningitis was estimated to be 1.1/1000 (0.11%) in the virus‑positive group and 3/1000 (0.30%) in the three groups.  2640 and 1320 children received MMR vaccination in September and October, respectively. Twelve children in the virus‑positive group, 10 in the serum‑positive group and 6 in the clinical group received vaccination in these 2 months.  The incidence of virus‑positive, serum‑positive and clinical meningitis in these 2 months was 3/1000 (0.3%), 2.5/1000 (0.25%), and 1.5/1000 (0.15%), respectively (total, 7.1/1000 (0.71%))."[20]

We have a letter from the Japanese Department of Viral Disease and Vaccine Control which indicates that from April 1993 the use of the MMR vaccine (all types) was stopped in Japan and that vaccines would be available only in their monovalent form (i.e. single virus)[21]

Comment:

       The Japanese findings indicate that adverse  reactions to these types of MMR vaccine were up to  78  times as frequent as our Government's Chief Medical Officer of Health  has admitted[22]. If those figures are correct, then the vaccine is more dangerous than the illness; and it does not give a great deal of confidence that the Government has got its figures (or information about safety or side effects) right.  Note also that this article was published in March 1991. Yet the two brands of MMR implicated with these side effects were not withdrawn until September 1992, some 18 months later.

       Indeed TRIVIRIX (a MMR vaccine containing the Urabe strain virus) was withdrawn in Canada in May 1990.[23]Why did the UK Government take till 1992 to withdraw it?

FONTI

https://www.merck.com/product/usa/pi_circulars/m/mmr_ii/mmr_ii_pi.pdf

http://www.vaccinationnews.org/DailyNews/February2002/MMRFactSheet.htm

http://www.who.int/vaccine_safety/initiative/tools/MMR_vaccine_rates_information_sheet.pdf

http://www.unicef.org/supply/files/MMR_Technical_Note.pdf