This article was released a week ago by a company that deals with genetic analysis and vaccine development, but it's pretty chilling reading if H7N9 ever develops sustained human-to-human transmission.

"Is H7N9 virus a 'stealth virus'"? reports this company's findings that the H7N9 virus has an unusually low number of epitopes.

Epitopes are the unique protein bits that present on the virus envelope. It's what the human immune system "sees" and what antibodies target. Antibodies are also used for quick diagnostic tests. The human immune system could basically be tricked into letting the virus proliferate right under its nose until it's too late and the host is seriously ill.

Few epitopes suggests that vaccines will be difficult to develop and may provide little protection. I've already read elsewhere that H7 strain vaccines tend to provoke a poor immune response to people, even when much larger amounts of antigen (the substances that provoke an immune reaction) are administered in each vaccine dose to a person.

Imagine a pandemic situation where governments are struggling to manufacture enough vaccine to protect everyone as quickly as possible. Instead of a company being able to produce 100 million doses, it's possible that each flu shot would require several times more antigen than usual, thus resulting in a fraction of the 100 million flu shots it could normally produce.

The other alternative is that chemicals that hyperstimulate the body's reaction to a flu shot is added, i.e. adjuvants, so that less antigen needs to be included in each dose. Adjuvants have never been used in US flu shots before and there is some controversy around them. In Europe, the H1N1 vaccine Pandemrix containing the adjuvant AS03 has been strongly linked to hundreds of new cases of narcolepsy in several countries by multiple studies.

The low immunogenicity of H7N9 also means that it could be difficult to develop a cheap, quick diagnostic test if things heat up even more. If a pandemic situation arises, it will be important to distinguish pandemic cases from other illnesses, and that will be hindered by lack of a cheap, quick test for H7N9. That could mean, for example, that limited supplies of antiviral meds could be administered to people who are sick with something other than a pandemic flu.