I think the speed--i.e. the lack of it--in producing vaccines will create various problems. Obviously, just the fact that it usually takes 9-12 months to even produce a normal year's batch of seasonal vaccine means that people won't be able to rely on a vaccine for quite a while. That may force us to rely heavily on anti-virals but I fear that the pandemic flu would quickly develop resistance before any vaccine is ready.

And with so many people getting infected during a pandemic, that just increases the chance that the virus will mutate enough to make a vaccine that was started 9 months ago to be less than optimal by the time there's a significant inventory built up.

An efficient distribution network will still be at the mercy of production limits. When the FDA shut down that Glasgow vaccine manufacturing plant a few years ago, suddenly cutting off a huge chunk of our normal flu vaccine supply, there was quite a bit of talk about who should get the limited supply. Should first responders get first crack? The most vulnerable sub-populations? If the public has a perception (which may not be factual) of a lot of people dying then who knows what kind of panic could surround any sort of vaccination campaign.

And there is not that much vaccine producing capacity. What happens when the entire human population on the planet is suddenly clamoring for vaccine? What do we in the developed world do about countries which are too impoverished to effectively purchase/produce/distribute a vaccine?

Heaven forbid that the pandemic strain actually turns out not to be easily cultured. Some people love to criticize seasonal vaccines when they aren't an exact match. That's mostly because of the long lead time between the start of production and when flu season actually hits, but another major factor is whether a particular strain can even be cultured effectively. Some strains are notoriously difficult to produce so a compromise is to select a different but related strain and hope that there's some crossover protection.

If--that's a huge if--some H5N1 strain turns out to be the next pandemic disease to hit humanity, at least there's one FDA approved vaccine out there. It certainly won't be an exact match to the pandemic strain, but it may be close enough to give partial immunity until a better vaccine can be produced.