Three different viral strains, called Poliovirus. It is these, entering the body most often through the digestive tract, that cause the polio. The disease is particularly fearsome, so much so that it can potentially cause paralysis of arms and legs and can even be fatal.
Thanks to vaccination, theEurope is “polio-free”. But there are signs that are rekindling attention on the topic. The latest comes from surveys in various countries of the European Union wastewater samples positive for poliovirusall in the past few months. And for this reason the ECDC, or the European Center for Diseases Control and Prevention, invites us to keep our guard up. Let’s be clear. These “findings” could signal a potential circulation of viruses, but there have been no cases of human disease. However, precisely for these reasons, the European Centers for Disease Control themselves remind us of the importance of guaranteeing a high vaccination coverage in the general population and to continue to support surveillance systems.
The history of the vaccine
The research to develop a vaccine, several decades ago, was extremely rapid. In the 1948, a team of researchers led by John Franklin Enders at Children’s Hospital Boston, managed to successfully grow the human poliovirus in the laboratory. For this research, Enders himself, together with Thomas Huckle Weller and Frederick Chapman Robbins, received the Nobel Prize for Medicine in 1954. Their basic studies, in fact, were fundamental for the development of a vaccine.
The first to be made was the Salk vaccinedeveloped with the simplest technique, that of inactivating the virus through formol. Validated as early as 1954, this vaccine was then studied in the largest clinical study ever carried out in the world, on 1,800,000 children in the USA, Canada and Finland. The results arrived in 1955 and the pharmaceutical industries were already committed to producing this vaccine in large quantities: however it was not, at least at the time, a particularly valid vaccine because the protective efficacy from batch to batch. Then there was a sort of “coup de grace” to that vaccine because some cases of illness occurred linked to the administration of the vaccine itself. The USA continued to administer it, but in Europe and Italy work began on the other vaccine developed by Sabin: in this case the virus was not inactivated, but attenuated. The first tests showed that this protection was effective and Italy chose that vaccine for the population immunization program.
The great vaccination campaign in Italy
Those with gray hair remember how in our country polio was responsible for around 3000 cases of serious disability a year. Furthermore, in 1958 a large epidemic was observed with approximately 8500 cases. Then, in 1964, thanks to the availability of the vaccine, the immunization campaign. The prevention initiative took into consideration all children between six months and 14 years of age, because it was thought that above this threshold the population was immunized against the virus thanks to natural infection. The campaign included three appointments: in March he was vaccinated against the Polio 1 virus, in April against the Polio 3 virus and in May for polio 2. Protection against this strain was carried out last, given that it was less virulent and above all could interfere with responses to other viruses. Then a booster was carried out using a dose of trivalent vaccine.
Europe becomes “polio-free”
Thanks to the massive vaccination campaign, which continued in the following years, in Italy the last case of clinically detectable infection was recorded in 1983 after a progressive decline in the number of cases without any increase. We therefore eradicated polio before other countries, considering that Europe became “polio free” at the beginning of the third millennium.
It must be said that over the years Vaccination strategies have changed. The Sabin vaccine, in fact, had recorded very rare cases of VAP (an acronym for Associated Paralysis virus) in very large numbers, especially after the first dose. In the meantime, research has worked hard to improve the Salk vaccine, which became available again in its renewed and safer version in the early 1990s. For this reason, in that era, they returned to administering the Salk vaccine, which had a better security profile. Even today Salk is contained in the hexavalent vaccination, in association with other vaccinations, and represents an excellent defense against infection. The vaccine is therefore a fundamental aid.
How to protect yourself in Italy
In Italy, the prevention of polio is foreseen administration of four doses of vaccine. This is the Salk preparation (also called IPV), which contains killed and inactivated polio viruses. The first doses are administered in the first year of life, generally in a single injection together with other vaccines in the so-called hexavalent. The fourth dose is administered between 5 and 6 years of age, as a booster. A fifth dose has recently been added for adolescents. Today, according to the National Vaccine Prevention Plan – PNPV 2023-2025, the vaccination cycle includes 5 doses to be administered preferably at 2 months, 4 months, 10 months, 5-6 years and in adolescence. In general, vaccination protection is very high and is maintained over time.
