Prevention

Definitions & Key takeaways

Prevention refers to the actions taken to avoid or reduce the likelihood of a disease or condition from occurring. Prevention is more effective and less costly than treatment. There are three main types of prevention: Primary prevention: involves taking steps to prevent a disease from occurring in the first place Secondary prevention: involves early detection and intervention to prevent a disease from progressing Tertiary prevention: focuses on rehabilitation and management of a disease or condition to minimize its impact and prevent complications.

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In epidemiology, there are three different types of prevention—primary, secondary, and tertiary. To get a clearer picture of what each type of prevention is and when it occurs, let’s first take a look at a timeline of the natural history of a disease, and we’ll use cervical cancer as an example.
Cervical cancer is cancer of the cervix, and around 13 thousand women are diagnosed each year. Most cases of cervical cancer are diagnosed in women ages 35 to 44, though older women are also at risk.
In the natural history of a disease, the first step is the biologic onset of the disease. So, in the case of cervical cancer, this is when a group of cells in the cervix become cancerous and begin to rapidly divide, forming a tumor.
At this stage, the person probably doesn’t even realize that they have the disease, since they’re still asymptomatic. At some point later, symptoms will start to show, like vaginal bleeding after sexual intercourse, or having unusual vaginal discharge.
And at this point, the person might go to a health clinic to talk with someone about their symptoms, and they’ll be diagnosed with cervical cancer.
Finally, the person will receive some type of treatment, like radiation therapy or chemotherapy, and this will eventually lead to an outcome, like remission, or in severe cases, death.
Now, this progression can be split into two phases. The preclinical phase is the time between the biological onset of the disease and when symptoms start to show, and the clinical phase is the time between when symptoms start to show and time when therapy is complete.
Now, let’s talk about how prevention fits into this timeline. The first type of prevention is primary prevention, and it’s all about stopping the onset of disease.
And this is what you probably think of when you hear the word ‘prevention’, and one way to remember this is because primary and prevent both start with the letter P.
In primary prevention, you’re trying to ensure that the person never develops the disease in the first place, so it happens at the very beginning, even before the biological onset of the disease.
Oftentimes, primary prevention involves changes to a person’s lifestyle to avoid exposure to risk factors, or factors that make it more likely to get the disease.
For example, women who smoke are around twice as likely to get cervical cancer compared to women that don’t smoke, so smoking cessation is one primary prevention recommendation for women at risk of cervical cancer.
Another type of primary prevention is vaccination, because vaccination can reduce the risk of disease caused by certain viruses.
For example, the human papillomavirus, or HPV, is a group of viruses that can be spread through sexual contact, and it causes the growth of papillomas, which are commonly referred to as warts.
These papillomas grow on different parts of the body, including genitalia, and chronic infection by papillomas can eventually cause certain types of cancers, like cervical cancer.
Fortunately, vaccines like Gardasil 9 can protect against the 9 strains of viruses that cause around 90% of cervical cancers—now that’s an effective primary prevention strategy!
The next type of prevention is secondary prevention, and this is all about delaying progression once a person has the disease, but while they’re still asymptomatic.
So, secondary prevention happens between the biological onset and when symptoms occur, during the preclinical phase. Screening is the most common type of secondary prevention, and the goal of screening is to identify people in the early stages of disease and treat them, because typically, treatments are more effective when they’re given at earlier stages compared to when they’re given at later stages.
The gold standard screening procedure for cervical cancer is the pap test, or pap smear, and it involves collecting cells from the cervix and testing them for abnormalities.
One way to remember that secondary prevention involves screening is because they both start with the letter S. Now, one thing to keep in mind is that screening is only effective if the disease has progressed enough to be detectable, and this time period is called the detectable preclinical phase.
If a person is screened before the detectable preclinical phase, the disease won’t be identified, even though it’s already biologically active.
This is why routine screening is often an important aspect of secondary prevention. The third type of prevention is tertiary prevention, which is all about treatment, and the goal is to stop complications or health deterioration after the disease has been diagnosed.
In other words, tertiary prevention tries to improve the overall outcome for people that already have the disease. Usually, changes in lifestyle aren’t enough to combat the disease, and other treatments are necessary, like medications or surgery.
For example, chemoradiotherapy—which is a combination of chemotherapy and radiation therapy—is a common treatment for individuals with cervical cancer.
Alright, as a quick recap, there are three types of prevention—primary, secondary, and tertiary. Primary prevention is all about preventing the disease in the first place, and typically this is done by lifestyle changes or by vaccination.
Secondary prevention involves screening individuals in order to delay progression once a person has the disease, but while they’re still asymptomatic.
And finally, tertiary prevention is all about treatment, and the goal is to stop complications and improve the overall outcome for people that already have the disease.