In reality there is no red carpet that leads to a magic injection against covid. The interruption for a week of the experimental vaccine trials at the University of Oxford, after detecting a suspicious inflammation of the spinal cord in a vaccinated woman, has reminded that the path back to normal life is rugged. Many things can still go wrong. And the incident has also shown the hysteria that can be generated by following the development of experimental vaccines in near real time. In July the same Oxford trial was paralyzedafter another participant was diagnosed with multiple sclerosis after receiving a vaccine. The tests were resumed within days when it was ruled that it was a coincidence. The case did not go to the press and no one was alarmed.
In the world there are already 35 experimental vaccines being tested in humans and nine of them are in the final stretch, the so-called phase 3, in which the prototypes must prove that they are safe and effective in tests with tens of thousands of volunteers for months. Promising initial results do not guarantee anything. A phase 2 trial with more than 100 people in 1995 showed that an experimental vaccine from the American pharmaceutical company Chiron against the genital herpes virus induced a hopeful immune response. In phase 3, with 2,400 volunteers already, those vaccinated were infected with the genital herpes virus just as those not vaccinated. The history of medicine is replete with phase 3 failures .
“I think there will be surprises. There always are. And not just in the next few months, but in one or two years, ” warns American pediatrician Paul Offit , co-inventor of the oral RotaTeq vaccine, which helps protect babies against diarrhea and vomiting caused by the rotavirus. The regulation to guarantee the safety of vaccines is so demanding that the big fiascos are counted on the fingers. Offit is the author of a book about one of them, The Cutter Incident (Yale University Press). In April 1955, more than 200,000 children in America received a defective polio vaccine. The Cutter laboratory, a family business, had not inactivated the live virus and there were 40,000 cases of polio, 200 children with paralysis and a dozen deaths.
“The Cutter incident was a manufacturing problem. It was 65 years ago. Now we are much better at making vaccines. I think production won’t be a problem, “says Offit, director of the Center for Vaccine Education at Children’s Hospital of Philadelphia. The pediatrician emphasizes that many of the most advanced experimental vaccines against COVID are not based on the most classical strategies – such as using inactivated viruses, in the case of polio; or attenuated, against measles, mumps and rubella – but instead employ new technologies never commercialized. “There will be a learning curve,” says Offit.
77% of the 1.3 billion doses that the EU has already reserved are of five experimental vaccines that use new strategies: three are made with the genetic code of the virus that of the German company CureVac, that of the American company Moderna and that of the consortium of the German BioNTech and the American Pfizer) and two use genetically modified common cold adenoviruses (that of the University of Oxford and that of the American multinational Johnson & Johnson ). “We are going to try to defeat the coronavirus with strategies with which we have no commercial experience. There is much to learn in the next two years ”, emphasizes Offit, who suggests a future of continuous braking to analyze alleged adverse effects.
Experts at the Brighton Collaboration – an international organization to ensure the safety of vaccines – have been working for months to discard one of scientists’ biggest nightmares: that some injections enhance COVID instead of preventing it. It is a paradox that has already been observed in some experimental vaccines against other coronaviruses, such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). Some vaccinated mice and ferrets underwent an overreaction of their immune system when they were later infected with these coronaviruses.
“To date, no potentiation of the disease associated with covid vaccines has been reported,” said Dr. Paul-Henri Lambert , from the Center for Vaccination of the University of Geneva (Switzerland), at a recent meeting of the Brighton collaboration. However, he warns, tests in monkeys have been done so far with “a very limited number of animals” and “with little follow-up time.” The surveillance continues.
“I think that most experts, although they are cautious and remain vigilant, do not see the potentiation of the disease as a probable problem,” says British statistician Stephen Evans , former president of the International Society of Pharmacoepidemiology. Evans is concerned about cases of Guillain-Barré syndrome , a rare disorder in which the human body’s own defenses attack the nervous system, causing muscle weakness and even paralysis. The syndrome, which usually disappears in a few weeks, is associated with infections by viruses or bacteria, although it can also be triggered by vaccinations, according to the WHO . The seasonal flu vaccine is linked to one Guillain-Barré case per one to two million of vaccinated people.
But what worries Evans most is not the unlikely adverse effects, but the very likely ghoulish coincidences that repeatedly paralyze clinical trials. Virologist Florian Krammer , from Mount Sinai Hospital in New York, recalled these days that one of his vaccine trials was interrupted by a traffic accident suffered by one of the participants. “We do not want to abandon a vaccine for fear of something that is a coincidence. That will be the greatest danger to global health ”, alerts Evans, from the London School of Hygiene and Tropical Medicine.
Pediatrician Paul Offit tells in The Cutter Incident that the 1955 disaster had a positive effect. Laws have been tightened and today vaccines are the safest drugs. Polio has prevented 18 million children worldwide from becoming paralyzed, according to WHO estimates. Before the vaccine, Offit recalls, the single threat more feared than polio was the atomic bomb.
