Long‑term immunity after a 6‑month‑old MMR vaccine (live attenuated) in infants: follow‑up of antibody levels 1‑3 years after routine vaccination
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Mumps Virus Rit 4385 Strain is a live attenuated vaccine virus, meaning it is a weakened form of the mumps virus that cannot cause the disease in healthy people but can still trigger an immune response. The full registry name is MUMPS VIRUS RIT 4385 STRAIN (LIVE, ATTENUATED) DERIVED FROM FROM THE JERYL LYNN PRODUCED IN CHICK EMBRYO CELLS. It is derived from the Jeryl Lynn strain of mumps virus and grown in chick embryo cells.[4]
This mumps strain is not used alone. It is a component of combination vaccines against measles, mumps and rubella (MMR) and, in some products, also varicella (chickenpox). In the trial registry it appears under the product name MEASLES, COMBINATIONS WITH MUMPS AND RUBELLA, LIVE ATTENUATED.[1] The substance is already authorised as a medicine in the European Union, and in two product records it is part of a fixed combination.[1]
According to the registry data, this substance is recorded as the test substance in two trials, while in the other two trials it appears as part of the vaccine being compared.[1]
As a live attenuated virus, Mumps Virus Rit 4385 Strain works by mimicking a natural mumps infection without causing disease. When the vaccine is injected, the weakened virus multiplies to a limited extent and is recognised by the immune system. This leads to the production of antibodies and immune memory cells that can protect against future exposure to wild mumps virus.[4]
The clinical trials measure this immune response by testing blood samples for immunoglobulin G (IgG) antibodies against mumps virus. The primary outcome in one trial is the seroresponse rate to mumps at day 43 after vaccination, meaning the proportion of children who develop a protective antibody level.[3] Another trial measures IgG concentrations against mumps at day 43.[4] The substance is classified in the therapeutic area of virus diseases in the registry.[1]
Mumps Virus Rit 4385 Strain is used for the prevention of mumps as part of MMR or MMRV vaccines. The authorised trials study it in the following settings:
In the trials, the vaccines containing this mumps strain are given as an intramuscular injection, meaning into the muscle. The registry lists the route of administration as intramuscular injection.[1] The dose in the trial records is 0.5 millilitres.[3]
One trial specifically compares intramuscular administration of an MMR vaccine against subcutaneous administration, which is injection under the skin. This comparison is designed to test whether the intramuscular route produces an immune response that is not inferior to the subcutaneous route.[3]
Four Phase 3 trials involving this mumps strain are currently authorised. All are interventional studies, meaning participants receive a vaccine and are then followed over time. None of the trials have reported results yet, as they are all in the authorised stage.
The trials cover three main areas. The largest trial, with 1,209 participants, studies a combined measles, mumps, rubella and varicella vaccine in healthy children aged 15 months to 6 years.[4] A trial with 994 participants studies MMR and chickenpox vaccination in healthy children aged 12 to 15 months.[3] A trial with 160 participants focuses on children and adolescents up to 18 years who have been treated for cancer.[1] A follow-up study with 1,000 participants examines long-term immunity after early MMR vaccination at 6 months of age.[2]
The primary outcome in three of the four trials is the antibody response to vaccination, measured around day 43 after the injection. This includes the seroresponse rate, which is the proportion of participants who develop a protective level of antibodies, and the geometric mean concentration (GMC), which is the average antibody level in the group.[3][4] One trial measures the difference in antibody levels before and after revaccination in children treated for cancer.[1] The follow-up study measures measles neutralising antibodies 1 to 3 years after routine MMR vaccination at 4 years of age, using a plaque-reduction neutralisation test.[2]
The trials enrol children of different ages. Two trials include healthy infants and young children: one from 12 to 15 months and one from 15 months to 6 years.[3][4] One trial includes children and adolescents aged 0 to 18 years who have been treated for childhood cancer.[1] The follow-up study includes children who previously took part in a trial where they received an early MMR vaccine or placebo at 6 months of age.[2]
No supplementary sources with side effect information were provided for this substance. The authorised trials will collect safety data, but no results are available yet.
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