The second wave and the vaccine

Countries in the Northern Hemisphere start pre-winter vaccination drive

Attendant prepares a dose of vaccine in a Chinese university hospital

Weeks ago, the United States and China started vaccination drives against the influenza A, H1N1 virus, of swine origin, that caused the flu pandemic in the first half of 2009 and created panic in many countries. Health authorities worldwide consider immunization the chief means of preventing swine flu deaths and of containing the spread of this virus, which started in the Northern Hemisphere even before the onset of winter and is likely to become the chief cause of flu in upcoming years.

Despite the confidence of health administrators in immunization, in countries such as the United States, part of the population is skeptical about having the vaccine. The same feeling that the virus awakened at the beginning of the year is what underlies this doubt: fear. If before people feared the virus’s aggressiveness, now they question the vaccine’s safety and fear its side effects. This is so because, even before trials for safety and effectiveness had been completed, the FDA (the United States Food and Health Administration) released the production and application of two types of H1N1 vaccines: one in injectable form, made from inactive viruses and suitable for any person aged 1 or above; and another in breathable form, made from attenuated viruses and recommended for healthy people aged 2 to 59. As these only protect against swine flu, they are being applied along with the seasonal flu vaccine.

Danielle Ofri, a professor at the New York University Medical School, published an article in November in the New England Journal of Medicine describing the contradictory behavior of people seen at the Bellevue hospital, the oldest one in the United States. At the onset of the epidemic, fear of this unknown virus drove them to demand a vaccine that did not exist. However, now that it is available, most people, being less anxious and more used to the virus, refuse to take it.

Experts have no doubt that the vaccine works, although some disagree as to the level of protection it provides. “Even if the vaccine doesn’t protect 100% of the people, it should protect at least some 75%”, states Edison Durigon, head of the Virology Laboratory at the Biomedical Sciences Institute of the University of São Paulo. According to him, those who have the vaccine may even catch the flu, but it will be less severe. “The vaccine will only lose its effectiveness if the epidemic’s predominant virus variety undergoes very drastic genetic changes, which is rare”. Should this occur, the loss of efficacy will become known in a while, after more people have been vaccinated and the level of protection provided by the vaccine is analyzed.

Up to mid-November, the World Health Organization (WHO) estimated that 65 million people in 16 countries had already taken the H1N1 vaccine. In one report, the WHO stated that in China 11 million people were vaccinated, with 15 cases of serious side effects being recorded and two deaths, although the latter did not necessarily result from the immunization. As the vaccine production will be insufficient for all (WHO expects world production to reach 3 billion doses a year), the priority is to immunize those who are at particular risk: children from the age of one, people with serious diseases and healthcare professionals. In Brazil, where the H1N1 death rate was 0.8 per group of 100 thousand people (the rate of seasonal flu is 0.5 per 100 thousand), the swine flu vaccine is expected to be available before the winter of 2010.