Expert reaction to vaccines recombining to form viruses

July 15, 2012

12 July 2012

A study in Science found different vaccines used to control an

infectious disease in chickens have been able to recombine to generate

new virus strains. The resulting new viruses have been responsible for

significant outbreaks of disease and death in farmed chickens.

“To my mind, the paper does not take into account sufficiently the

possibility that recombination may have occurred between the vaccine

strains and normal virus strains circulating in Australia at that time.

It seems much more likely that the vaccine would encounter the normal

circulating virus. The normal virus(es) present in Australia are not

included in their Fig 1A.

" Having said that, it is obviously the case that live attenuated

vaccines have the potential for recombination. The use of vaccines is

always a risk-benefit calculation. There can be a variety of side effects

from vaccines; many are well known. For example, we stopped immunising

people against smallpox because the adverse reactions began to exceed the

benefit as the disease was eradicated.

" Vaccines have been one of the great success stories of medicine and

the type of important technicality raised in this article should not be

allowed to detract from the enormous health benefit generally provided by

vaccines. "

Prof Openshaw, Director of the Centre for Respiratory Infection

(CRI) at the National Heart and Lung Institute, Imperial College London,

said:

" This is a highly plausible study, showing the importance of

close monitoring and investigation of outbreaks of respiratory disease in

livestock. Viruses are highly adaptable and will exploit every

opportunity for self-improvement. We need to be constantly on the lookout

for novel outbreaks and to intensify our study of the benefits and risks

of well-intended vaccination programmes. "

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