Two different viruses will lay millions low this winter
IT HAS taken seven months for the vaccine intended to protect people from the potentially deadly H1N1 strain of influenza to start trickling onto pharmacy shelves. The first doses are now being made available in America. Supplies will remain limited for months to come. In the meantime, the vaccine—both the killed version that is injected and the attenuated live version that is given as a nasal spray—is being rationed to those reckoned most in need.
That means children, pregnant women, nursing staff and those who could easily infect other vulnerable groups—especially infants and people with weakened immune systems. Strangely, the new H1N1 strain of virus does not strike the elderly anything like as much as seasonal flu does. This relative immunity—the opposite of what normally happens each winter—suggests that they may have been exposed to something similar in the past.
After camping out in the southern hemisphere during the northern hemisphere’s summer, the worrisome new virus—originally called “swine flu” when first reported in March in Mexico—has circled the globe and returned north with a vengeance. More than 375,000 cases have been reported to the World Health Organisation and 4,500 people have died in the current pandemic. The most recent influenza pandemic, of Hong Kong flu, swept the world in 1968-69 and killed 1m people. The last pandemic caused by an H1N1 strain was in 1918-20, when Spanish flu took an estimated 50m-100m lives.
Part of the delay in delivering an H1N1 vaccine is a result of it not being just another seasonal flu. It is additional to, and entirely different from, the usual bout of influenza that kills upwards of 250,000 people around the world each winter. Manufacturers have still had to produce the usual “trivalent” vaccine for this year’s seasonal flu, plus a wholly different vaccine for the more deadly H1N1 strain. To protect themselves (and those around them) people should take both the seasonal flu vaccine and, when they can get it, a dose of the H1N1 vaccine as well.
The big question is, will they? A recent poll by Consumer Reports, a citizens’ advocacy publication, found that 43% of Americans were still undecided about getting vaccinated against H1N1. Your correspondent despairs at the half-truths and conspiracy theories that abound. One popular talk-show host even tweeted that folks who get vaccinated against the new H1N1 strain were idiots. So much for medical wisdom in 140 characters.
Urban myths about the dangers of influenza vaccines have lingered in America since the country’s panicked reaction to a swine-flu scare in 1976. A vaccine was rushed out and a quarter of the population hurriedly vaccinated before the programme was cancelled, after the successful containment of the outbreak on the army base where it had started. But that was not before a number of patients developed a neurological illness called Guillain-Barré syndrome as a result of taking the vaccine and 30 people died from complications that they would not otherwise have suffered. Despite the millions of lives saved by flu vaccines since—and the introduction of far stricter regulations governing the trial, approval, manufacture and distribution of vaccines—irrational fears about their safety persist across a broad swath of the American population.
Certainly, today’s added precautions have contributed to the delay in producing the new vaccine. So far, four vaccines against the H1N1 virus have been approved in the United States under the same process used by the Food and Drug Administration (FDA) for seasonal flu vaccines.
Whether H1N1 or seasonal, influenza vaccines are made using hens’ eggs as factories. Millions of fertilised eggs are inoculated with small doses of flu virus and incubated to grow the large quantities of virus needed for a vaccination programme. When ready to be harvested, the tops of the eggs are sliced off and the virus collected. Sometimes it is killed to make it harmless, split to rid it of its fatty envelope and then purified to form the final dead vaccine. In other cases, the virus is merely crippled, so it cannot cause infection, and is then used as a nasal spray. Such attenuated live vaccines can be more effective, but are costlier to produce.
The trouble with using hens’ eggs for making killed or attenuated vaccines is that production cannot be ramped up quickly in an emergency. It takes months to get the hundreds of millions of eggs needed into production.
Earlier this year, the European Union approved a seasonal flu vaccine called Optaflu that is grown in large vats of living cells, instead of hen’s eggs—in much the same way as vaccines for chickenpox, polio and measles are made. The advantage of this approach is that it can be scaled up simply by adding more bioreactors to the plant. Novartis, which manufactures Optaflu, is currently building a plant in North Carolina, but has yet to get FDA approval for its cell-based vaccine.
The technology has not stopped there. Instead of injecting proteins from a flu virus into a person’s body, why not inject just the micro-organism’s genes? Cells in a person’s body would then read those genes and start producing their own vaccine-like proteins. Engineering a vaccine this way would be even quicker than producing one from a cell culture.
Influenza’s genes are composed of RNA, not the more familiar DNA, but DNA is the more stable of the two molecules, so is preferred for making vaccines. (The genetic codes of RNA and DNA are slightly different, but are freely interchangeable.) Several years ago, researchers at the University of Pittsburgh made an artificial DNA vaccine for the H5N1 bird flu virus that was greatly feared at the time. To do so, they generated the DNA coding for the virus’s hemagglutinin gene(the H in a virus’s name)—which translates into a protein found on the surface of all influenza viruses. Finally, they spliced the hemagglutinin gene into a common-cold virus and used that to make a vaccine.
Injected into animals, the genetically engineered vaccine provided 100% protection against bird flu. The whole process—from receiving the genetic sequence by e-mail from the Centres for Disease Control and Prevention to testing the finished vaccine in animals—took roughly 30 days. Clinical trials using the technology are currently under way. Even so, it could be years before this sort of vaccine is deemed safe and effective enough for use in people.
Further off still is the ultimate goal: a universal flu vaccine that can be given just once in childhood and provides a lifetime’s protection against all forms of influenza. Your correspondent has no doubt that such a one-shot flu vaccine will one day be given to infants along with jabs against chickenpox. Alas, it is unlikely to happen in his own lifetime.