I hope this WHO FAQ helps clarify the rumors and misunderstandings about the new swine flu vaccines.
The only safety problem remains (as shown in this FAQ) is the potential risk of developing Guillain-Barré syndrome (GBS), which was suspected to be associated with 1976 swine flu vaccines.
But even for the 1976 case, the GBS rate is 1/10^5 according to the WHO FAQ (but said to be only 2/10^6 according to CDC, USA, as reported by a recent MSBC news report, see below).
As a reference, the incidence rate od GBS in the general population is 1-2/10^5, and the rate linked to flu vaccine is 1/10^6.
For the new swine flu vaccines administered currently in USA, as of 12 November, only 5 (or 6) cases of GBS have been known out of 40 million doses of vaccines, which corresponds to a much lower rate 6/(40*10^6)=0.15/10^6.
See http://www.msnbc.msn.com/id/33845867/ns/health-cold_and_flu for a recent news report.
Note that for all the suspicious cases linked to 1976 flu vaccines, it is still unclear if the vaccines are the real cause, since the natural incidence rate of GBS is even higher or at the same level.
See a recent publication on this topic:
“Prepandemic” Immunization for Novel Influenza Viruses, “Swine Flu” Vaccine, Guillain‐Barré Syndrome, and the Detection of Rare Severe Adverse Events. David Evans, Simon Cauchemez, Frederick G Hayden. The Journal of Infectious Diseases 2009;200:321–328
In the MSNBC news report, it is also said that only 68 serious adverse events have been received by the CDC, which corresponds to a rate 68/(40*10^6)\approx 1/10^6, on par with the seasonal flu vaccine.
On the other hand, it was estimated by the US CDC that more than 4000 people have died due to swine flu during April to 17 October, which corresponds to a mortality of at least 4000/(300*10^6)>10/10^6>>1/106, where 300*10^6 is the whole population of USA.
It is obvious the real mortality should be even much higher, if the denominator is the number of all swine flu cases instead of the whole population.
So, as a whole, if a person has a high risk of being infected, it is better to take the vaccine to reduce the risk of death.