04 September 2013

Flu shot: do no harm!

American researchers working under the leadership of Dr. Hana Golding from the Center for Biological Analysis and Research in Bethesda, Maryland, injected piglets who had never previously encountered the flu virus with a vaccine against one of the strains of the H1N2 virus. Some time later, the animals were exposed to a rare strain of the pathogen H1N1, which caused the pandemic of the so-called "swine flu" in 2009.

Vaccination ensured the appearance in the animals of a wide range of antibodies blocking the H1N2 virus. However, these antibodies not only failed to protect them from H1N1 infection, but also contributed to the penetration of viral particles into lung tissue, exacerbating symptoms and increasing the likelihood of developing pneumonia and other secondary respiratory infections. In unvaccinated pigs of the control group, pneumonia proceeded more easily and fewer other complications of the underlying disease were observed.

A more detailed study showed that the antibodies produced when the vaccine is administered to the H1N2 virus are unable to bind to the key region of the H1N1 virus particle and, accordingly, cannot destroy or neutralize them. On the contrary, they promote the penetration of viral particles into lung cells and the subsequent formation of new viral particles.

The authors emphasize that the identified effect should be taken into account when developing a universal vaccine that can protect a person from all strains of the influenza virus. They also warn that the demonstrated pattern may not apply to humans. Moreover, the vaccines used in the study were made from whole killed virus particles, whereas human vaccines include only their components.

However, the data obtained add significance to the results of a study conducted in Canada, which showed that during the outbreak of H1N1 influenza, people who underwent seasonal flu vaccination were at greatest risk of developing the disease.
Article by Surender Khurana et al. Vaccine-Induced Anti-HA2 Antibodies Promote Virus Fusion and Enhance Influenza Virus Respiratory Disease is published in the journal Science Translational Medicine.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on Medical Xpress materials:
Vaccination may make flu worse if exposed to a second strain.


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