If you want a visual and great explanation on the concept of herd immunity look up the chain of infection and read a little bit about it.
Basically for a comment reply, the gist is that there are 6 main components that are necessary for disease to spread. If you break any of the links in that chain then you prevent the spread of infection. The more links you break the harder the spread for infection.
Each infection is different and acts in different ways and our own man made preventions and such all have different levels of effectiveness.
As an example, dysentery is severe diarrhea caused by pathogens in contaminated food and water. As long as you prevent the contamination of food and water this essentially goes away. This is something we essentially "cured" through improved hygiene hundreds of years ago.
For something like influenza which has VERY hit or miss immunization coverage and that is spread easily by respiratory droplets that are coughed or sneezed up it is better to have a combination of approaches which is why they recommend the influenza vaccine for those at risk of coming into contact or those who are at risk of serious complications if they get influenza. They also recommend people covering coughs and sneezes, not touching your face, social distancing, and washing hands frequently.
Herd immunity is something you want when the spread of something is not easily controlled by breaking other links in that chain. Measles is an airborne virus. It has super small particles that travel easily and the infection can be EXTREMELY dangerous and even deadly. You can't exactly just cover your cough (mode of transmission) and not touch your face (portal of entry) because you can literally just breath that virus in from the air. This is where the idea of herd immunity comes in. If enough people are vaccinated and able to effectively fight the virus and prevent it's spread it no longer has a host (reservoir) to hang out in. If you make enough people immune to being reservoirs, then people who are unable to get vaccines for whatever reason are at a much lower risk of becoming infected.
If you want a visual and great explanation on the concept of herd immunity look up the chain of infection and read a little bit about it.
Basically for a comment reply, the gist is that there are 6 main components that are necessary for disease to spread. If you break any of the links in that chain then you prevent the spread of infection. The more links you break the harder the spread for infection.
Each infection is different and acts in different ways and our own man made preventions and such all have different levels of effectiveness.
As an example, dysentery is severe diarrhea caused by pathogens in contaminated food and water. As long as you prevent the contamination of food and water this essentially goes away. This is something we essentially "cured" through improved hygiene hundreds of years ago.
For something like influenza which has VERY hit or miss immunization coverage and that is spread easily by respiratory droplets that are coughed or sneezed up it is better to have a combination of approaches which is why they recommend the influenza vaccine for those at risk of coming into contact or those who are at risk of serious complications if they get influenza. They also recommend people covering coughs and sneezes, not touching your face, social distancing, and washing hands frequently.
Herd immunity is something you want when the spread of something is not easily controlled by breaking other links in that chain. Measles is an airborne virus. It has super small particles that travel easily and the infection can be EXTREMELY dangerous and even deadly. You can't exactly just cover your cough (mode of transmission) and not touch your face (portal of entry) because you can literally just breath that virus in from the air. This is where the idea of herd immunity comes in. If enough people are vaccinated and able to effectively fight the virus and prevent it's spread it no longer has a host (reservoir) to hang out in. If you make enough people immune to being reservoirs, then people who are unable to get vaccines for whatever reason are at a much lower risk of becoming infected.