Rhiza Labs FluTracker Forum

"Swine flu vaccines under development by drugmakers may not provide immunity until the last week of November, too late to hold off outbreaks triggered by infected students returning to schools in the U.S. and Europe," Bloomberg reports.

So combining the following:
1. Vaccines too late to prevent large outbreaks at school starts (from article).
2. Many people will/already have been exposed and have immunity.
3. Mutation of H1N1 may occur before vaccines are available making them ineffective for new strain.
4. Vaccines rushed to production potentially having unforeseen side effects.

Are the current vaccines going to be effective/good idea?

Discussion and conclusions

Most cases described during the three pandemics of the 20th century and during seasonal influenza involve transient illness not requiring hospitalisation. Most deaths are described in the very young or the elderly or those with underlying disease. The 1918-1919 pandemic, however, was characterised by a high mortality rate in healthy young adults and an estimated CFR of 2-3% [5]. Even with a low CFR, seasonal influenza epidemics cause significant morbidity and mortality with an estimated three to five million cases of severe illness and about 250,000 to 500,000 deaths worldwide [6].

To date, the CFR attributable to the current H1N1 pandemic has been estimated at around 0.4%, based on surveillance data from Mexico and mathematical modelling [7]. This CFR is higher than that of average seasonal influenza but remains of the same order of magnitude. Whether this will change before the expected epidemic peak in the northern hemisphere in the autumn is unknown.

Evaluating CFR during a pandemic is a hazardous exercise. Aside from the issue of whether or not a death has been caused by the influenza infection, cases tend to be detected initially among severely ill patients with a higher probability of dying. This leads to an overestimation of the computed CFR at the beginning of an outbreak. The computed CFR subsequently evolves as the case reporting strategy is adapted to the situation. When the situation no longer requires exhaustive reporting of cases, the computed CFR will inevitably increase and grossly overestimate the true CFR.

Specific investigations or modelling allow for a more accurate estimation of the number of cases. As of 27 May 2009, there had been 820 confirmed cases in New York City, of whom two had died, resulting in a computed CFR of 0.2%. A telephone survey estimated that in fact 250,000 cases had occurred in that city of 8.3 million inhabitants, resulting in an estimated CFR of 0.0008% [8,9]. In the United Kingdom (UK), there were 28 deaths reported for a documented 10,649 cases as of 16 July 2009 and a computed CFR of 0.26%. However, health authorities estimated that the cumulative number in the UK on that date was 65,649 cases and 28 deaths, which corresponds to an estimated CFR of 0.04% [10].

The pandemic, however, is far from over, and deaths will unfortunately continue to occur. As in previous pandemics, available data show that age groups are not equally affected. Compared to younger age groups, the elderly seem to be protected from infection to some extent, perhaps due to previous exposure to strains akin to influenza A(H1N1)v virus [11-13]. When infection does occur, however, the percentage of deaths in elderly cases seems to be higher than in others. Initial estimates available from Mexico for the period until 16 July 2009 showed that the risk of death in aged cases (over 50 years) was higher (6% deaths among cases) than in children (0-1% deaths among cases aged 0-19 years) and young adults (2-4% deaths among cases aged 20-49 years) [3].