H1N1 Vaccine Safety

There is just so much information available to us these days that it is often difficult to even know where to start when trying to answer a basic question.  One question that I have, as do many of my readers is…

How do they test the H1N1 Vaccine for safety?

If you follow the anti-vaccine crowd you would think that the FDA tests it on a few gerbils and then declare it safe for the entire U.S. population.  On the other hand, if you follow the pro-vaccine crowd you might think that the FDA is just short of God in the perfection of their safety testing practices.  I can assure you that neither is true.  Here is what I have been able to find…

The FDA

On September 15th, 2009 the FDA announced that it had approved the new H1N1 vaccine for use in the U.S.  While the FDA is useful for keeping harmful things out of the U.S. medical system, one should not confuse their approval with a seal of absolute safety.

In short, their decision to license and approve the vaccine for use is based upon …

”The H1N1 vaccines … undergo the same rigorous FDA manufacturing oversight, product quality testing, and lot release procedures that apply to seasonal influenza vaccines,” said Jesse Goodman, M.D., FDA acting chief scientist.

They go on to note that:

“All four [vaccine] firms  manufacture the H1N1 vaccines using the same processes, which have a long record of producing safe seasonal influenza vaccines.”

So to be clear, the FDA has licensed a product that meets certain manufacturing safety criteria, which is made in a similar manner (by the same companies) that produce the seasonal flu vaccine, which has a long track record of safety.

Safety trials are currently being conducted by the National Institute of Allergy and Infectious Diseases (NIAID) looking specifically at the safety of the new H1N1 vaccine in various populations.

Clinical Trials for Safety and Efficacy

Normal Healthy People

The vaccine is initially tested in healthy individuals aged 18-64.  If the vaccine has a good track record in this group of people then vaccine testing moves to more vulnerable populations – like pregnant women and children.

The initial trials started on July 22, 2009 and have currently enrolled over 500 patients.  Initial analysis of these 500 patients has not shown any serious adverse reactions and thus the trials are moving into the second phase -pregnant women and children.

Pregnant women

As of  September 1, 2009 pregnant women, in their 2nd or 3rd trimester, are being recruited to evaluate the safety of the vaccine.  A total of 120 women will be recruited for this safety study.  The study will last about one year and will evaluate the effectiveness of the vaccine for the women and their babies, as well as monitor for adverse reactions.

Children

As of the end of August, healthy children from the age of 9-17 are being recruited to evaluate the safety of the vaccine.  A total of 650 children will be enrolled in this study.  This study will assess the need for one shot or two, the effective dose of the vaccine, and monitor for adverse reactions.

In Summary

If you take all the studies and add up all the patients, there will be about 3000 patient who get enrolled in the safety studies.  You can bet that at the end of the the study the findings will be something like…

“The vaccine is safe and not associated with any serious adverse events.”

Understanding Serious and Rare Adverse Events

The astute reader will note there is a discrepancy in the numbers between the number of people tested and some historical accounts of the rate of serious adverse reactions.  If you remember, back in 1976, the “bad” vaccine was associated with about a 1 in 80,000 risk of getting GBS (a neurologic disorder).  That means that if you gave 80,000 people the vaccine, roughly one would have this serious adverse reaction.  Thus if you test this new vaccine on just 3000 people, it would not be surprising if there were no serious and rare side effects noted.  All we can say is that the rate of serious adverse reactions is less than 1 in 3000.

Unfortunately the only way to find serious and rare adverse reactions is to release it to the general public and monitor closely for those serious and rare adverse reactions.  The FDA (and others) are implementing a robust system to watch for these potential rare adverse events.

Comparing H1N1 to the Seasonal Flu

The new H1N1 vaccine is made by the same companies in exactly the same way as the Seasonl Flu vaccine.   Thus for the Seasonal Flu we have decades of experience and millions of vaccinated Americans to draw upon.  From this we can make one rational conclusion… The rate of adverse reactions to the H1N1 vaccine is likely to be similar to the rate of adverse reactions to the Seasonal Flu vaccine.

For the Seasonal Flu vaccine this is what I find:

1. Soreness, redness, or swelling at the site of the shot.
2. Fever
3. Body aches
4. Severe allergic reactions – less than 1 per million
5. Guillain-Barre Syndrome – less than 1-2 per million

Numbers 4 and 5 are so rare that is is difficult to determine a definitive link to the the vaccine (if one even exists).

Take Home Point

Once the vaccine is released (in early October) this is what we can say:

1. The overall rate of rare and serious adverse events is less than 1 in 3000.
2. The rate of rare adverse events is likely to be similar to that of the Seasonal Flu.
3. The FDA is monitoring closely for adverse events.

From what I have read (and based on my opinion) there is little doubt in my mind that there is any substantial risk associated with the H1N1 vaccine.  For pregnant women and people with chronic medical conditions, the consequences of getting the Flu seem significant.  For us, my wife is planning to get the vaccine and we will follow closely the reports that come out once the vaccine is given more widely.

Stay Informed

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References

Clinical trials:

Pregnant women

Pediatric Trials

Initial Trial

Other article of interest:

FDA Release

FDA Safety Monitoring