Live And Dead Vaccines

[rizenstar]

Just wondering if anyone can tell me which they prefer and why you prefer it, benefits of each etc

[Guest Tess32]

This is from Dr. Jean Dodds -

Killed Versus Modified Live Vaccines

Most single and combination canine vaccines available today are of MLV origin. This is based primarily on economic reasons and the belief that they produce more sustained protection. A long-standing question remains, however, concerning the comparative safety and efficacy of MLV versus killed (inactivated) virus vaccines. A recent examination of the risks posed by MLV vaccines concluded that they are intrinsically more hazardous than inactivated products. The residual virulence and environmental contamination resulting from the shedding of vaccine virus is a serious concern. More importantly, the ability of new infective agents to develop and spread poses a threat to both wild and domestic animal populations. The controversy in weighing the risks and benefits of MLV versus killed vaccines is building. Vaccine manufacturers seek to achieve minimal virulence (infectivity) while retaining maximal immunogenicity (protection). This desired balance may he relatively easy to achieve in clinically normal, healthy animals but may be problematic for those with even minor immunologic deficit. The stress associated with weaning, transportation, surgery, subclinical illness, and a new home can also compromise immune function. Furthermore, the common viral infections of dogs cause significant immunosuppression. Dogs harboring latent viral infections may not be able to withstand the additional immunological challenge induced by MLV vaccines. The increase in vaccine-associated distemper and parvovirus diseases are but two examples of this potential. So -- why are we causing disease by weakening the immune system with frequent use of combination vaccine products? After all vaccines are intended to protect against disease. It is well-recognized by experts in the field that a properly constituted killed vaccine is always preferable to one of MLV origin. Killed vaccines do not replicate in the vaccinated animal, do not carry the risk of residual virulence and do not shed attenuated viruses into the environment. On the other hand, MLV vaccines are capable of stimulating a more sustained protective response. So what does the future hold here? Veterinarians, scientists, breeders and owners need to voice their concern and discontent with the present industrial vaccine practices. We need to urge manufacturers to seek alternatives. Even if killed vaccines are proven to be somewhat less efficacious (produce lower levels or less sustained protection) than MLV products, they are more safe. All killed vaccines on the market today have passed current efficacy and safety standards in order to be licensed for use by the USDA. The issue is to what extent being more effective elicits a benefit rather than a risk. The future will evolve new approaches to vaccination including sub-unit vaccines, recombinant vaccines using DNA technology, and killed products with new adjuvants to boost and prolong protection. These are not simple solutions to a problem, however, because early data from recombinant vaccines against some human and mouse viruses have shown potentially dangerous side-effects by damaging T-lymphocytes. Contributing factors were shown to be the genetic background of the host, the time or dose of infection, and the makeup of the vaccine. We are obviously still a long way from producing a new generation of improved and safe vaccines. In the meantime, we need to return to using killed products whenever they are available and should consider giving them more often (twice yearly rather than annually) for high-risk exposure situations. Vaccines, while necessary and generally safe and efficacious, can be harmful or ineffective in selected situations.