Vaccinations

Vaccines have become the number one prevention method against diseases. Vaccines are either attenuated or inactivated. Attenuated vaccines are categorized as such due to their ability to replicate in the host because they are created with a weakened form of the pathogen. Since the vaccine is created from the actual pathogenic microbes it causes a real immune response to the mild disease it causes, resulting in immunity against future strains of the disease that try and infect the vaccine recipient. Inactivated vaccines are still able to create immunity despite the fact that they can’t replicate. These vaccines are generally weaker because they are unable to actually amplify the initial dose, so although it’s good that they are unable to actually become pathogenic, many times boosters are required. 

Polio is an example of a disease that has been nearly eradicated due to the use of vaccines. Polio can be caused by serotypes 1, 2 and 3 of the poliovirus – a single-stranded, non-enveloped, RNA virus. In about 1% of the cases, polio could result in paralysis, especially if acquired young. Two vaccines were created in order to attempt to stop the spread of the disease – IPV or Inactivated Polio Vaccine and OPV or Oral Polio Vaccine. IPV and OPV are a good example of how attenuated and inactivated vaccines differ in their functions. IPV was created using all 3 serotypes of the disease and it successfully lowered the disease rate, but it required a series of vaccinations and didn’t have a high secretory IgA response. Secretory IgA (SIgA) response is important because SIgA blocks pathogens from binding to epithelial recpetors and then traps them and helps to remove them from the body through actions like coughing, sneezing and a runny nose. But the OPV was created using an attenuated version of the disease which resulted in better SIgA response. This meant that the OPV could stop the virus before it even attached to the epithelial cells, resulting in the complete stop of the spread of the disease and therefore better herd immunity. The only problem now was the fact that the OPV could possibly become pathogenic, making it more dangerous to use. But since IPV doesn’t stop the spread of the pathogen to feces (as the disease is acquired through the fecal-oral route), it can’t be used solely. So a combination of the two vaccines have been used to eradicate polio. In the US, children were first given IPV for immunity then given OPV as a booster and for SIgA response ability, until the disease was considered eradicated and OPV use was discontinued. 

As of October 2019, according to the World Health Organization serotypes 2 and 3 had been globally eradicated. In order for a strain to be considered eradicated, it must go undetected for 3 years. The only problem is that recently there have been vaccine-derived poliovirus type 2 infections that have surfaced in the Philippines. This type of infection occurs due to the circulation and mutation of the excreted virus from people who have not been given a complete series of the vaccination or have been inadequately vaccinated. Since type 2 had been deemed eradicated in 2015, the vaccine in the Philippines changed over to a OPV that only contained serotypes 1 and 3, leaving the population susceptible to the vaccine-derived type 2 poliovirus. The Philippines have been given a huge shipment of vaccines that contained just type 2. A series of factors have influenced the possible re-emergence of this eradicated disease – a decreased trust of vaccinations, “inadequate delivery at the community level, too few primary care immunisation sessions, and difficulties in accessing hard-to-reach areas in the archipelago”. All of these together have harmed the health of the people of the Philippines and is a trend that can also be tracked in many other places. I think that this case in the Philippines has proved that even if we think a disease is completely gone, we can never be too careful and should always take extra precautions against infection.

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