VOf the 4 vaccines that have been tested for their effectiveness against HPAI (highly pathogenic avian influenza) H5N1 bird flu, 2 appear to be effective under laboratory conditions. “The so-called HVT-H5 vaccines provide protection against disease symptoms in laying hens and prevent the spread of the virus,” said Nancy Beerens, head of the National Reference Laboratory for avian influenza.
The vaccine study was conducted at Wageningen Bioveterinary Research, part of Wageningen University & Research (WUR), in collaboration with Utrecht University, Royal GD and WUR, on behalf of the Dutch Ministry of Agriculture, Nature and Food Quality (LNV).
3 new and 1 old tested
In the study, 3 modern types of vaccines were tested for their effectiveness in laying hens. It concerns the HVT-H5 vaccine from Ceva Sante Animale, the HVT-H5 vaccine from Boehringer Ingelheim Animal Health and the DNA vaccine from Huvepharma.
In addition, the Nobilis vaccine from Merck Sharp & Dome was included in the study. This is an older type of vaccine and the only vaccine currently registered in the Netherlands. The effectiveness of the Nobilis vaccine against the current bird flu virus has not been tested before.
“It was important in the selection of the vaccines that we can distinguish between animals that have been vaccinated and animals that have antibodies because they have had an infection. This distinction can be made with the 3 modern vaccines; these comply with the so-called DIVA principle,” explains research leader Nancy Beerens. These are vaccines that are already on the market in other countries, or that are in an advanced stage of development. However, whether these vaccines work against the current HPAI H5N1 virus and can prevent the spread of the virus between laying hens, had not been tested before.
Study design
Each vaccine was administered to 10 laying hens. Subsequently, 5 chickens were infected with the bird flu virus; these were placed in a house together with 5 chickens that were not infected. For example, it was investigated whether the virus would be spread from the infected chickens to the non-infected animals.
Both HVT-H5 vaccines proved to be 100% effective in controlling morbidity and mortality after infection with the HPAI H5N1 virus. This is in contrast to the other 2 vaccines where disease was observed. The study showed that both HVT-H5 vaccines prevent virus spread between chickens. For these vaccines, the calculated reproduction number (R-value) in the trial was 0.
Follow-up
“Our study shows that 2 HVT-H vaccines are effective under laboratory conditions and protect against both disease symptoms and virus spread. These vaccines comply with the DIVA principle and on that basis are good candidates for further research in practice,” says Beerens. The 2 HVT-H5 vaccines can be administered in the egg or to day-old chicks in the hatchery.
Vaccines may work less well in the field than in research facilities. “It is therefore important to investigate whether the vaccines work well under practical conditions, how long the vaccines protect and whether a booster shot is needed.”
Field study will start this summer
The Dutch Ministry of Agriculture, Nature and Food Quality is commissioning a field study that will start this summer. In addition, the vaccines still need to be registered in the Netherlands and the European Union. “There are still some hurdles to overcome, but the results of our research are an important first step towards vaccination against the bird flu virus in poultry farming,” says Beerens.