It's necessary to start vaccination for Polio now?

It’s necessary to start vaccination for Polio now?

It’s necessary to start vaccination for Polio now? Does Polio really come back? Scientists call for vigilance.

In July, a 20-year-old man in Rockland County, New York, was diagnosed with polio, a highly contagious, disabling and potentially fatal disease caused by the poliovirus (hereafter referred to as polio). disease.

On June 22, the UK Health Security Agency announced that poliovirus had been detected several times in sewage in London, UK, but no cases had been reported. During the same period, Israel reported that the virus was also found in sewage in Jerusalem.

It's necessary to start vaccination for Polio now? Does Polio really come back? Scientists call for vigilance.

The world’s top scientific journals, Nature and The Lancet, recently published an article saying that these events herald an unexpected and worrying development in humanity’s long-standing battle against polio: poliovirus reemerges in sanitary conditions In well-developed developed countries; the actual spread and scale of the virus may be more widespread than is currently understood; thus potentially more cases of paralysis in unvaccinated individuals.

According to WHO, polio mainly affects children under the age of five. Irreversible paralysis occurs in 1 in 200 cases, and 5% to 10% of paralysis cases result in death from respiratory muscle paralysis. There is no cure for polio, but it can be prevented with safe and effective vaccination.

Polio is also one of the few diseases that can be eradicated, and the number of cases caused by wild poliovirus has fallen by more than 99% since 1988, from an estimated 350,000 cases at the time to just six reported in 2021.

But as long as one child is infected with poliovirus, children in all countries remain at risk of contracting the disease. Failure to eradicate it in all countries could lead to a global resurgence of the disease. And sluggish vaccination rates in recent years due to the Covid-19 pandemic could undo years of hard-won progress.

Epidemic in many countries

Before traces of the poliovirus were found in New York’s wastewater, a series of ominous signs were already emerging around the world.

Malawi, Africa announced its first case in 30 years in February, a 3-year-old girl who became paralyzed after contracting poliovirus.

The case can be traced back to the case reported in Pakistan. Pakistan has reported 14 cases this year.

In March, Israel reported its first case of polio in a child since 1988. The virus was also detected in several other children, but showed no symptoms, and almost all cases were unvaccinated.

In June, British authorities declared an “event of national concern” after poliovirus was found in sewage.

In July, poliovirus was detected in New York’s sewers after paralyzed cases, suggesting the virus may actually be spreading more widely.

Notably, the infected man in the U.S. was not vaccinated and did not travel abroad during his possible exposure to the virus, suggesting he contracted it domestically, after the U.S. had declared polio eradication.

“No country in the world is immune to polio,” Zulfiqar Bhutta, a global health researcher at Aga Khan University in Karachi, Pakistan, was quoted as saying by Nature. Inter-related.”

Vaccines to blame?

Genetic analysis showed that the viruses in the three developed countries were all vaccine-derived poliovirus type 2 (VDPV2), meaning they were a variant of the virus derived from an oral vaccine.

There are three types of wild polioviruses.

In 2015, the WHO announced the eradication of type 2 and in 2019 the eradication of type 3. Only type 1 poliovirus is still not eradicated, and it is circulating only in Pakistan and Afghanistan.

There are currently two widely used polio vaccines: the inactivated vaccine (IPV), which is administered intramuscularly, and the oral vaccine (OPV), both of which are certified by the WHO as safe and effective.

Oral vaccines have been used in many countries since 1988 and have the advantages of being inexpensive, easy to administer and administer, and better at protecting entire populations at risk of transmission, and have played a major role in helping developing countries eradicate polio. effect.

But the oral vaccine has long been controversial because it contains a weakened form of the live virus.

In extremely rare cases, attenuated viruses also sometimes mutate into live transmissible viruses in immunocompromised populations, causing outbreaks in unvaccinated populations through the faeces of vaccinated people, especially in poor sanitation and vaccination low level.

More and more countries that have eradicated polio are now turning to inactivated vaccines to avoid such risks. Last year, the WHO also announced that it was developing a new, more stable and safe oral vaccine.

It is unclear how far the poliovirus has spread in the US, UK and Israel. All cases were linked to people with unvaccinated or weakened immune systems, the CDC said. Most U.S. adults were vaccinated as children and are adequately protected.

Call for vigilance

Polio is the disease most likely to be eradicated in humans after smallpox. The disease once terrified countless families and paralyzed hundreds of thousands of children around the world each year.

In 1955, after the first vaccine was introduced, global polio cases fell by 99% – from 350,000 paralyzed cases in 1988 to six reported in 2021.

There is little risk from the virus for people who are vaccinated.

But scientists point out that the pandemic has disrupted routine vaccination schedules in many countries, making them more vulnerable to a polio resurgence, and there is an urgent call for countries to increase vaccination rates, especially among children.

The Nature article pointed out that the discovery of poliovirus reemergence in countries such as the UK and the US should be a wake-up call, and a comprehensive analysis of the factors contributing to virus transmission in settings with only inactivated vaccines, high national vaccine coverage and good sanitation should be made detection.

Polio and Covid-19, as well as monkeypox, which was just announced this year, are the only three currently considered by WHO as “public health emergencies of international concern” (PHEIC).

It is worth noting that a public health emergency of international concern is not the same as a large-scale global outbreak. In contrast, polio has been virtually eliminated from the world and is currently endemic in only a few countries.

But with the goal of polio eradication looming, any sustained outbreak in a still fragile country would be a catastrophic setback.

As a result, WHO has maintained polio at this highest alert level since 2014 and continues to update its concerns.