Crucial role of polio research and 2 vaccines
The inability to culture polio in non-nerve cells was a major roadblock to developing a polio vaccine.
John F. Enders and his team made it possible for the poliovirus to be mass-produced for vaccine research
Jonas Salk made the first successful vaccine using Enders’ method to grow the virus.
He inactivated the virus by treating it with formaldehyde, and injected it into his test subjects.
The fragments of the inactivated virus were able to induce immunity in their bodies.
Importantly, since the vaccine was introduced into the muscle, it generated systemic immunity.
Soon after Salk made his inactivated polio vaccine (IPV), Albert Sabin developed another vaccine that contained live polio strains weakened by growing them serially in macaque cells, making them unfit for human infection.
Since Sabin’s vaccine contained live virus particles, it had to rely on its natural mode of infection and was therefore administered orally.
This was the oral polio vaccine (OPV)
Since the OPV went into the stomach, it induced a powerful protective mucosal immune response right where the virus would have to begin its infection.
The OPV had multiple advantages over the IPV.
First, the vaccine induced a protective response at the viral entry site — the gut— allowing it to provide a much greater degree of protection relative to the IPV.
Second, the OPV was administered orally and didn’t require syringes or trained personnel for its administration.
Occasionally, the weakened virus in the OPV would revert, and do the very job it was designed to prevent: cause polio.
On the other hand, the IPV, while being a less potent vaccine, contained inactivated virus particles and carried no risk of causing vaccine-induced polio.
Challenges
Polio eradication is one of the top priorities of the World Health Organisation (WHO).
Since Africa was declared polio-free in August 2020, the wild poliovirus has been restricted to rural pockets of Afghanistan and Pakistan.
But according to a recent report in Science, the virus is beginning to reappear in big cities in these two countries
This reemergence is a result of vaccine hesitancy due to misinformation, conflict, poverty, and limited access to these isolated regions.
The WHO’s Global Polio Eradication Initiative is thus set to miss its deadline of eradicating polio by the end of 2024.
COMMENTS