Considerations for a Potential SARS Vaccine
• Pursuing a vaccine against SARS will require multiple approaches, a significant effort, and will require collaboration among molecular biology, virology, immunology, animal experimentation.
• A vaccine needs to be administered pre-exposure, induce protection against clinical disease and perhaps against infection and transmission, be given in few doses, elicit neutralizing antibody response, be safe and immunogenic, and be manufactured efficiently on a large scale.
• Robust mucosal immune response may be needed and is difficult to achieve with many vaccines.
• Antigenic variation of SARS CoV needs to be monitored.
Animal CoV Vaccine Results
• Mucosal immunization strategies are required to protect newborn animals.
• Partial protection is demonstrated with live or inactivated vaccines in some cases, but is not durable.
• Subunit vaccines are not particularly effective except for priming and boosting.
• Antigenic variation is a problem with IBV.
• Live vectors show promise in some models.
• Feline infectious peritonitis vaccine enhances disease.
Evaluating Possible Approaches
• For inactivated whole-virus vaccine, the method of inactivation may be important to preserve the native structure; these may not provide long-lasting immunity and require multiple boosting.
• Recombinant subunit vaccine will require adjuvant and likely mucosal delivery.
• Live vectors or replicons may be problematic because of anti-vector immunity.
• Live-attenuated virus may be the best approach to induce mucosal and systemic immunity, or could be part of a priming and boosting regime, and would not have manufacturing issues.
• DNA alone has not been a successful vaccine and faces regulatory issues.
Timeline and Cost
• An aggressive timeline puts a "go/no-go decision" at 18 months after beginning vaccine development.
• Development would cost 60 to 100 million dollars and five to six years at a minimum.