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Breakthrough COVID-19 cases and the game-changing Delta variant

What first responders need to know about the likelihood of side effects from the vaccine vs. the virus, plus new infection rates


While the initial COVID-19 variant (Alpha) has always been more contagious than the common flu – and with longer-term consequences for many – the Alpha variant’s rate of infectivity was 50% higher than the flu.


Some people will get COVID-19 even if they are vaccinated. So what’s the point of getting the vaccine if you can still get the virus – deemed a “breakthrough infection”? The key: People who have been vaccinated are far less likely to contract COVID-19 than those who aren’t vaccinated. But there’s more to the story, particularly as it relates to side effects and how the Delta variant is changing the game.

First responders under the microscope

Doctors Jeff Burgess and Alberto Caban-Martinez are two well-known fire service researchers who are collaborating in a large prospective cohort of healthcare workers, first responders and others on the frontline of the pandemic to study the impact of the vaccine. The project – titled Healthcare, Emergency Response and Other Essential Workers Surveillance Study (HEROES); Research on the Epidemiology of SARS-CoV-2 in Essential Response Personnel (RECOVER) – has led to a national collaboration that is shedding light on the virus, vaccines, and their effectiveness among first responders.

First, the study has found that less than 10% of individuals who have received both doses of an mRNA vaccine experienced a breakthrough infection.

The study also found that firefighters in particular are at 60-100% higher risk of contracting the infection than healthcare workers. While data is still emerging, it seems that it is not patient/responder interactions that are driving the infection risk; rather, it is the communal living of the firehouse that is driving infection. While risk mitigation procedures are clear when treating patients, how to eliminate risk when you live with your colleagues one-third of the time – and ultimately share many of your exposures with them – is more of a challenge.

Vaccine side effect concerns

Still, concerns remain about the vaccine. Despite extensive research about the safety and efficacy of vaccines, there are still skeptics who point to the speedy rollout as a sign that they are not ready for use.

One example of concern is the recent warnings about Guillain-Barre syndrome in individuals who received the vaccination. It should be noted that this increased risk has been primarily a concern among adenovirus vector vaccines and has not been linked to mRNA vaccines, like the Moderna and Pfizer vaccines.

What often goes under-discussed is the risk of the side effects in comparison to the risk of the same outcome associated with COVID-19 infection. Specifically, while approximately 100 cases of Guillain-Barre syndrome are documented and under investigation among the 12 million vaccines given in the United States, the rate of Guillain-Barre syndrome among those infected with COVID-19 appears to be much higher. The same is true of nearly every side effect that has been raised as a concern related to the vaccines; this includes everything from fertility and impotence to cardiovascular complications – the rates of the side effects are actually higher among those infected with COVID-19 than those who received the vaccine.

Read next: ‘Warp speed’ vaccine: Addressing firefighters’ concerns over the quick vaccine rollout

Game-changing Delta variant

With the initial variant of COVID-19, some argued that the risk of infection was not that high, so the risk of side effects from the vaccine was not worth the risk, given they believed they were not likely to contract the infection. Enter the Delta variant.

As of the writing of this article, 65% of cases in the United States are caused by the Delta variant – a staggering number considering that it was first identified in the U.S. in March 2021. While the initial COVID-19 variant (Alpha) has always been more contagious than the common flu – and with longer-term consequences for many – the Alpha variant’s rate of infectivity was 50% higher than the flu. The Delta variant’s rate of infectivity is 50% higher than the Alpha.

Given no vaccines and no attempts at mitigation, the average person infected with COVID-19 infected 2.5 additional people. The same situation with the Delta variant will lead to between 3.5 and 4 people being infected.

It’s not over

For those still deciding whether to get vaccinated, the choice is between risking the low chance of experiencing a side effect or the higher chance of experiencing the same issue as a symptom of infection.

So, what does this mean for the fire and emergency services? Put simply, this pandemic isn’t over for us. The vaccine is providing some reprieve, but areas with high rates of vaccine deliberators are seeing significant increases in infection rates.

Another issue the fire service needs to be aware of is that the Delta variant is infecting kids at a higher rate than previous variants. Researchers studying the viral load of the Delta variant compared to the original Alpha found the viral load was 1,000 times higher with the Delta variant. Given the infections occurring through firehouse living, crews and firefighters who are not vaccinated need to be aware of the risks posed to their families.

In all, the work is not finished for those on the front line.

Stay safe and healthy.

Read next: ‘Long-COVID’: Understanding the long-term risks following a COVID-19 diagnosis

Sara Jahnke, PhD, is the director and a senior scientist with the Center for Fire, Rescue & EMS Health Research at the National Development & Research Institutes - USA. With over a decade of research experience on firefighter health, Dr. Jahnke has been the principal investigator on 10 national studies as well as dozens of studies as a co-investigator. Her work has focused on a range of health concerns, including the health of female firefighters, behavioral health, risk of injury, cancer, cardiovascular risk factors, and substance use, with funding from the Assistance to Firefighters Grant R&D Program, the National Institutes of Health and other foundations. Jahnke has more than 100 publications in the peer-reviewed medical literature. Awards include the 2019 Endowed Lecture at the annual conference of the American College of Epidemiology; the 2018 President’s Award for Excellence in Fire Service Research as well as the Excellence in Research, Safety, Health & Survival Award, both from the International Association of Fire Chiefs (IAFC); and the 2016 John Granito Award for Excellence in Firefighter Research from the International Journal of Fire Service Leadership and Management. Connect with Jahnke on LinkedIn, Twitter or via email.