PAS: Incidence Of Aseptic Meningitis In Mumps Vaccine Recipients Is Lower Than In Patients With Natural Mumps Infection
By Adi Ferrara
SEATTLE, WA -- May 5, 2003 -- Children
vaccinated against mumps have a lower risk of developing related
aseptic meningitis compared with children who contract natural mumps
infection, according to a Japanese study presented here May 2nd
at the Annual Meeting of the Pediatric Academic Societies.
"The safety of vaccination is essential
but vaccine adverse effects should be discussed based on risk and
benefit relationships," said Dr. Takao Nagai, of the Nagai Pediatric
Clinic in Takamatsu, Japan, who presented the findings for the
Vaccine Study Group of the Society of Ambulatory and General
Pediatrics of Japan.
Dr. Nagai and the other 10 principle
investigators in this study hope that, based in part on their study,
Japan would resume measles-mumps-rubella (MMR) vaccination of
infants in 2 years.
Japan halted administration of live
attenuated MMR vaccine in 1993, due to a high incidence of aseptic
meningitis that year. This higher-than-expected rate was probably
due to an adverse reaction to the particular virus strain used in
the vaccine, said Dr. Nagai. Japan currently licenses three viral
strains for monovalent vaccine production. Low population coverage
with a monovalent mumps vaccine, caused mainly due to the high cost
of the vaccine, results in annual mumps outbreaks.
To compare the incidence of aseptic
meningitis associated with natural mumps infection and mumps
vaccine, Dr. Nagai and his colleagues followed previously healthy
children 18 years or younger for 15 days of infection or 30 days
post-vaccination.
After confirming mumps infection in
study participants, wild or vaccine virus strains were determined by
genome sequencing. Viral infection was confirmed through virus
isolation or evaluation of throat swabs using reverse transcription
polymerase chain reaction. In patients with severe symptoms of
aseptic meningitis, a lumbar puncture confirmed aseptic meningitis
by a pleocytosis of more than 15 cells in the cerebrospinal fluid
(CSF).
They enrolled 1,085 children with
confirmed cases of natural mumps infection and 17,912 vaccine
recipients. Of the participants with natural mumps infection, 13
(age range 1-10 years) developed aseptic meningitis. CSF was
examined in 10 of these children (three samples were not transported
to the laboratory for testing), and wild-type mumps virus was
detected in seven of the 10 CSF samples.
The incidence of infection-associated
meningitis was 1.2%, and 0.65% for virologically confirmed
meningitis (virus detected in CSF). There were 12 cases of
meningitis in vaccine recipients (age range 1-16 years old). One
case could not be confirmed by pleocytosis, and one case was caused
by enterovirus. Of the remaining 10 cases, vaccine strain virus was
isolated in eight patients. No aetiological agent could be found for
the remaining two cases.
The incidence of vaccine-associated
meningitis was 0.06%, and for virologically confirmed cases it was
0.04%.
It is clear from these numbers that the
risk of aseptic meningitis in non-vaccinated individuals is greater
than in vaccine recipients, according to the researchers.
A follow-up question during the
presentation pointed out that since lumber puncture was carried out
only in patients with severe symptoms, the actual percentage of
aseptic meningitis in children with natural infection is probably
higher.
The team did not compare the severity
or sequelae of aseptic meningitis in the vaccinated versus the
naturally infected group.
The study was sponsored by the Society
of Ambulatory and General Pediatrics of Japan.
[Study title: The Incidence of Aseptic
Meningitis in Mumps Patients and Mumps Vaccine Recipients in Japan.
Abstract: 1761.]