Why do you think the Alberta government decided to provide HPV vaccine funding for boys, as well as girls, in Grade 5? (
5 years ago
Answered By Michael D
The rationale behind support for a general HPV vaccine is an attempt at eliminating the disease from the general population. If a significant enough portion of the population is immunized, individuals who are not immunized will be protected from the infection, due to the simple fact that there is proportionally less people that will come into contact with them that are carriers of the disease. This is called a Herd Immunity Threshold, and depends on the contagiousness of an infection.
This herd immunity can be demonstrated by a simple equation of probability. There are more complex formulas derived from calculus operations, but the following is easy enough to explain with simple algebra:
R * S = 1
Where R is the rate of infection, determined by observation (often difficult to determine exactly), and S is the proportion of the population susceptible to infection. Total probabilities always add up to 1, so our equation is nicely balanced. S can be described of in terms of a probability as well, since there are some members of the population, such as in our example:
R * (1-p) = 1
Where (1-p) replaces S, as p is the percentage of the population that are immune. This equation can then be rearranged to:
1 - (1/R) = p
The “p” is the threshold proportion of the population that needs to be immune in order to stop transmission of the disease.
What you should take away from that if you don’t want to read through it all, is that a higher R rate is associated with higher infection rate, thus the amount of individuals that need to be immunized for any sort of herd immunity needs to be higher (higher p value close to 1). By immunizing enough individuals, it creates a feedback loop where infection rate of R also lowers in value, which pushes the level needed for Herd Immunity (p) even lower. This can only be attained by pushing past that threshold.
For HPV, it’s statistically shown that it has a growing infection rate even compared population increase. This could be because of a key difference with HPV compared to many other diseases - it’s with you for life, and if you are exposed at all before immunization you have it for good. One mistake early in life may cause a lot of trouble down the road - unless you happened to be vaccinated. Hence, immunizing through the public education system, where most of the population passes through at some point. By immunizing people prior to any exposure, the threshold Herd Immunity may be surpassed and the infection rate will decrease
As for why AHS should cover this, it’s a public health risk. Preventative medicine such as this is essential for cost effective solutions for public health issues. Public schools have always been an effective place to implement public health policies due to the large amount of exposure, reaching the broadest segment of society. In this case, the spread of HPV is not only responsible for the well publicized risks of cervical and ovarian cancer, but also the various other health issues. This is a terrible cost of life, in addition to the burdening the medical system.
As for covering males as well as females, HPV rates are actually statistically 5% higher in males than in females, meaning that there is a sizeable portion of males that are carriers compared to females. This means that in order to achieve that threshold value effectively (p), it is rational not only to immunize not just females, but males who may eventually carry this disease to their significant others. As it often is symptomless for many people, this fact often flies under the radar before it’s too late.
If you'd like to read more about R values, I found this lovely paper: https://wwwnc.cdc.gov/eid/article/25/1/17-1901_article
5 years ago
Answered By Michael D
The rationale behind support for a general HPV vaccine is an attempt at eliminating the disease from the general population. If a significant enough portion of the population is immunized, individuals who are not immunized will be protected from the infection, due to the simple fact that there is proportionally less people that will come into contact with them that are carriers of the disease. This is called a Herd Immunity Threshold, and depends on the contagiousness of an infection.
This herd immunity can be demonstrated by a simple equation of probability. There are more complex formulas derived from calculus operations, but the following is easy enough to explain with simple algebra:
R * S = 1
Where R is the rate of infection, determined by observation (often difficult to determine exactly), and S is the proportion of the population susceptible to infection. Total probabilities always add up to 1, so our equation is nicely balanced. S can be described of in terms of a probability as well, since there are some members of the population, such as in our example:
R * (1-p) = 1
Where (1-p) replaces S, as p is the percentage of the population that are immune. This equation can then be rearranged to:
1 - (1/R) = p
The “p” is the threshold proportion of the population that needs to be immune in order to stop transmission of the disease.
What you should take away from that if you don’t want to read through it all, is that a higher R rate is associated with higher infection rate, thus the amount of individuals that need to be immunized for any sort of herd immunity needs to be higher (higher p value close to 1). By immunizing enough individuals, it creates a feedback loop where infection rate of R also lowers in value, which pushes the level needed for Herd Immunity (p) even lower. This can only be attained by pushing past that threshold.
For HPV, it’s statistically shown that it has a growing infection rate even compared population increase. This could be because of a key difference with HPV compared to many other diseases - it’s with you for life, and if you are exposed at all before immunization you have it for good. One mistake early in life may cause a lot of trouble down the road - unless you happened to be vaccinated. Hence, immunizing through the public education system, where most of the population passes through at some point. By immunizing people prior to any exposure, the threshold Herd Immunity may be surpassed and the infection rate will decrease
As for why AHS should cover this, it’s a public health risk. Preventative medicine such as this is essential for cost effective solutions for public health issues. Public schools have always been an effective place to implement public health policies due to the large amount of exposure, reaching the broadest segment of society. In this case, the spread of HPV is not only responsible for the well publicized risks of cervical and ovarian cancer, but also the various other health issues. This is a terrible cost of life, in addition to the burdening the medical system.
As for covering males as well as females, HPV rates are actually statistically 5% higher in males than in females, meaning that there is a sizeable portion of males that are carriers compared to females. This means that in order to achieve that threshold value effectively (p), it is rational not only to immunize not just females, but males who may eventually carry this disease to their significant others. As it often is symptomless for many people, this fact often flies under the radar before it’s too late.
If you'd like to read more about R values, I found this lovely paper: https://wwwnc.cdc.gov/eid/article/25/1/17-1901_article