The recent announcement by the World Health Organisation that no serious and unexpected adverse effects have been seen in the nearly 65 million people who have been vaccinated for the 2009 influenza A(H1N1) in 16 countries is encouraging. Apprehensions about the vaccine’s safety were raised by the medical fraternity in a few countries and parents were unwilling to get their children vaccinated. The vaccine was seen as a new and experimental drug hurried along in fast-track mode, tested on a small number of volunteers, and followed up for an inadequate duration. Though fast-tracking flu vaccines is routine as the basic ingredients remain the same, a frontal objection was raised by The New England Journal of Medicine in an editorial: “any association of uncommon adverse events with this vaccine cannot be ascertained in studies of this size.” Reports from following up millions of people after vaccination have now put at rest the safety concerns. The side effects — swelling, redness, pain at the site of injection, fever, and headache — were the common and anticipated ones; they resolved themselves spontaneously soon after vaccination. Although a small number of deaths occurred in people who had been vaccinated, investigations have shown that no direct link could be established between vaccination and the deaths; underlying medical conditions were found to have caused these deaths. The risk of Guillain-Barre syndrome — a rare autoimmune disorder that damages the peripheral nervous system, and in rare cases can cause permanent paralysis or even death — following vaccination was one of the most feared serious adverse effects. According to the WHO, fewer than ten suspected cases of this rare syndrome were encountered and all the patients recovered eventually.
According to the world body, the safety profiles were no different in inactivated and live attenuated vaccines. Likewise, there was little difference between adjuvant (a substance added to a vaccine to improve its effectiveness) and non-adjuvant vaccines. The safety profile of adjuvant vaccines, which the WHO recommends, is particularly important. The use of adjuvant reduces the amount of vaccine used in a dose, which means a greater number of people to be vaccinated under constrained circumstances. While A(H1N1) adjuvant vaccine is used in many countries in Europe, and adjuvant has been routinely used in seasonal influenza vaccine for over a decade, the U.S. has not approved it. Despite the safety profile of A(H1N1) vaccine matching the seasonal influenza vaccine, the need for continuous monitoring of those vaccinated cannot be over-emphasised.