| 摘要 |
<p>The present invention is concerned with a vaccine which is capable of protecting poultry against Infectious Bursitis infections, characterized in that it contains an Infectious Bursitis virus which has the combined properties of upon administration to a chicken causing a reduction in the size of the bursal size, expressed as bursa/body weight ratio, of less than 55 % and the capability to protect poultry having an ELISA antibody titer of at least about 500 and with viruses having the above characteristics.</p> |
