How Effective is Efficacy? 

By: Danielle Lane  |  May 11, 2021

By Danielle Lane, Opinion Editor

In the past year we have learned dozens of new terms and phrases. From epidemiology to quarantine to social distancing, the pandemic has brought a new vocabulary into our cultural lexicon. Many of these words and phrases are self explanatory; a mask mandate is a requirement to wear a mask, social distancing is a nice way to tell someone to get away from you. Other terms are less clear, for example what is mRNA technology? Or what does an epidemiologist do?

Recently there have been a few newer terms which have caused confusion.  A few weeks ago, after being fully vaccinated a family friend (who was also fully vaccinated) was diagnosed with Covid-19. This news sent panic throughout the community of vaccinated people who had felt that they were completely immune to the virus. What did this mean for them? Wasn’t the vaccine supposed to promise a return to normalcy? What was the point of getting the vaccine if it wouldn’t create a Danny Phantom-esque force field around you to protect against Covid-19? And the biggest, most important question on my mind; how effective is vaccine efficacy? 

When I first started hearing the term “efficacy” I assumed it meant the same as effective.  Therefore if the Covid vaccines have an average efficacy of 97% wouldn’t that mean that I’m 97% protected against the virus? Not quite. Efficacy is essentially the ability to reach the goal of the treatment. Therefore for when we say that the vaccine has a 97% efficacy rate that means that those who have received the vaccine have a 97% less chance of getting the virus than those who have not received the vaccine.  But wait, how is that different from effectiveness? While efficacy and effectiveness are very similar and their differences can be confusing, it is important to understand their differences so that you may speak intelligently about the vaccine and make the best educated decision for yourself.  

When we talk about a vaccine being effective what we mean is out of everyone who took the vaccine (or treatment) how many still got sick?  For example the yearly influenza vaccine has an effectiveness of 40-60%, this means that only 40-60% of the people who get the flu shot will not get the flu.  Due to the fact that effectiveness of the vaccine can be affected by many real world confounding variables such as pre-existing conditions, work environment, and location, it is still important to get vaccinated, even if the effectiveness may seem low.

So now that we know the basic definitions of these two words what does that mean in terms of the vaccine? In all of the clinical trials of the various Covid vaccines that are now authorized by the FDA (Federal Drug Administration) for emergency use, there has been a severe decrease in serious (hospitalized) cases of Covid. Therefore while the vaccine doesn’t completely protect someone from actually getting Covid-19, it does severely decrease the chances of ending up in the hospital on a ventilator as a result of the virus. 

You may be asking yourself, now that I’m fully vaccinated does that mean I get to forget all of the new terms and phrases that became so widely used in the past year? Unfortunately, not yet.  Until we reach herd immunity with about 70-80% of the population being vaccinated against Covid-19, many of the year long protections will probably still need to remain in place in order to protect those members of the community who either can’t or won’t get vaccinated. Due to the fact that the vaccine doesn’t completely eliminate the chances of getting the virus, only the chances of developing serious side effects of the virus, it is important to continue to wear masks and social distance from people in most settings. While once vaccinated you will most likely never be sick with Covid, you could still be a carrier and therefore it is important to continue to protect those around us. The CDC has thoroughly outlined when and where fully vaccinated individuals can relax on Covid restrictions.  

Even though “masks mandatory” and “social distancing” will probably remain a part of our vocabulary for a little bit longer, the good news is that the more people who get vaccinated the closer we are to returning to total normalcy. If you’re able to get vaccinated please consider reading about vaccination science and process and making an informed decision that not only protects you but those around you.

I would like to thank Dr. Daniel Kimmel for an amazing semester and for being such an epic Epidemiology professor.