COVID epidemiology explained: Promising news about vaccines

A COVID-19 vaccine is a goal for addressing the pandemic. Last week there was promising news that both Pfizer and Moderna had positive results for a Phase 3 vaccine candidate and will be applying for Emergency Use Authorization (EUA) with the Food and Drug Administration (FDA). If approved, both pharmaceutical companies plan on mass producing the vaccine for public consumption. This could make the vaccine available to the general public in 2021.

Despite the positive news about vaccine development, other studies point out a challenge. It appears that public acceptance to the vaccine is limited. To reach herd immunity, which limits spread and prevents outbreaks, experts believe we would need to vaccinate 70% of the population. The highest receptiveness observed in surveys in just over 60%. These findings highlight a challenge in addressing infectious diseases that we’ve been seeing for decades. In explaining the challenge, let’s start with an overview of how vaccines works.

When you get a vaccine, we expose your immune system to an antigen in order to initiate a response from our immune system to create antibodies. An antigen is a deactivated pathogen, enzyme, or DNA segment that is unique to an infectious agent. The antibodies created after this exposure are used to fight off the infectious agent when it’s in our system. These antibodies enable our immune system to launch a strong response towards a specific infectious disease. When we give people a vaccine, our body develops the ability to recognize and respond to an infectious disease before we get sick. Without a vaccine, we have to endure the disease and the symptoms that come with it until our immune systems can recognize an antigen and develop the antibodies. With a vaccine, our immune system is able to clear an infection before we experience any symptoms. The discovery of vaccines along with improved access to clean water and sanitation were key in our battle against common infectious diseases in the early 20th century and increased life expectancy by decades.

The success of vaccines in preventing the spread of a number of infectious diseases led to policy changes that have reached pushback over the past few decades. In 2020 there are a series of vaccines that we give to children during their first 24 months of life. The pushback against them has a variety of reasons. One is that mandating vaccination conflicts with individual freedom regarding health decisions. Opponents of this stance argue that opting against getting a vaccine compromises public health; since vaccines protect individuals and other community members from infection. Another common reason stems from debunked studies that drew a correlation between vaccines and autism. Despite being disproved, a lingering concern still exists; that all therapeutic drugs have side effects and risks. Most clinical interventions acknowledge risk while noting that the benefits outweigh them. This does not apply to vaccines that are given to people that are already healthy. Vaccine recipients and their children are then left with an odd decision. Do they expose a healthy person with a vaccine to prevent a disease they’ve likely never seen and risk side effects?

A commonly articulated rationale for the trending reduction in vaccination acceptance rests in perceived risk. Here we gravitate towards the Health Belief Model; which states that major factors in our health behavior centers around our perceived susceptibility and perceived severity. Essentially, having a low number of cases of diseases we vaccinate against decreases receptiveness. Ironically, vaccine success can lead to decreased receptiveness to getting it.

Decreases in common childhood vaccines have led to outbreaks of diseases such as measles in the past decade. Some work in educating the public about vaccines and dispelling myths may be necessary in the coming months. One promising finding in the data suggests high receptiveness to a COVID vaccine stemming from the number of participants in the clinical trials. Generally a Phase 3 clinical trial enrolls up to 4,000 participants but Pfizer’s trial enrolled over 40,000. Over the next few months, we will see how we can utilize this effective clinical measure in disease prevention in the middle of a pandemic.