Some parents may want to give one immunization at a time, but this option is not always available.
An individual vaccine can immunize against multiple diseases or even multiple strains of a disease, and breaking them down into separate shots isn’t always possible to do. Pharmaceutical companies often combine multiple antigens into their formulations either for convenience, or to increase the efficacy of the immunization.
- Monovalent vaccines Immunize against a single microorganism or a single strain of a microorganism.
- Multivalent vaccines Immunize against two or more strains of the same microorganism, or against two or more microorganisms.
When your child receives one injection, there could be multiple strains or vaccines in that one inoculation. For example, the pneumonia vaccine only protects against pneumococcal bacteria, but there are 7, 13, or 23 different strains of pneumococcus that the vaccine is intended to protect against, depending on which version of the shot received. Breaking these strains into different shots would make little sense because the strains are similar and separating them would entail dramatically increasing the number of injections required.
An example of a combination vaccine is the MMR. It is only one injection, but it is intended to protect against measles, mumps, and rubella. Because these are live virus vaccines for three very distinct illnesses, parents may express a desire to separate this shot into three different injections.
Internationally, the MMR vaccine can be separated into single components. For example, measles vaccination can be given without mumps or rubella. In the US, though, the measles vaccine is only available as a combination shot (MMR or MMRV).
Other vaccines are combined because one component, like the pertussis component of the DTaP, does not work as well if not combined. Although different variations are available for different age groups, the monovalent acellular pertussis is not available in the US, and diphtheria and tetanus components are given together worldwide.
In the United States, parents have limited options when it comes to separating some combination vaccines. For example, an individual measles vaccine or whooping cough vaccine is not available in the U.S. at this time. These immunizations are available as combination vaccines only.
Examples of vaccines that are offered as single, multiple or combined vaccines:
- Single strain: Hepatitis B, Rotavirus, Hib, Polio, Varicella, Hepatitis A
- Multiple strains: Pneumococcal, Influenza, HPV, Meningococcal
- Combination: DTaP, MMR
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