Influenza and Covid-19 Vaccine Risk and Benefit in 2024

We are now entering this fall’s season for influenza, a disease which has effectively always been with us, and our fourth winter with Covid-19.  We fortunately have good vaccines for each that substantially reduce severe infections and death, even though a vaccinated person may still become ill with either virus.

Vaccinations Are Recommended by Public Health Groups

The federal Centers for Disease Control and the Massachusetts Department of Public Health, as well as many other national and local medical groups, all recommend that everyone, adults and children (except infants), get the current influenza vaccine this fall and also the updated Covid-19 vaccine. I support those recommendations, as does the local town board of health to which I am elected.

The reason for these public health recommendations is the vaccines’ well documented and documentable benefits in disease mitigation and death reduction.

Weighing Risks and Benefits Individually

I had posted two months ago on the desirability and importance of getting the influenza and Covid-19 shots this fall. But I have read of and encountered sluggishness about getting the vaccines, which I believe does a health disservice to the sluggards and their families.

So I will now review the documented risks and benefits for each vaccine and disease to be sure accurate information is readily available for consideration. Each person can determine how much risk he or she wants to accept, but in each case the quantifiable risks of the disease, the quantifiable benefits of the vaccine, and the exceedingly low quantifiable risks of the vaccine, make it clear that the benefit-to-risk ratio is substantial.

Influenza

What Is the Risk of Influenza Infection?

CDC estimates that during the 2023-2024 season 40 million people were sick with influenza, 18 million people visited a health care provider for influenza, 470,000 had influenza-related hospitalizations, and 28,000 influenza-related deaths occurred. That is, about 1 person in 9 in the U.S. was ill with flu. The deaths were heavily weighted to older age groups and those with underlying conditions as well as to the unvaccinated. Though many cases are mild, even nonfatal infections can be debilitating for 5-7 days, as some of my unvaccinated patients found out each year. And, by the way, just a few years ago in 2017 the influenza death toll was 79,000.

What Is the Benefit of Influenza Vaccination?

In the same article, CDC estimates that last year influenza vaccination prevented 9.8 million influenza-related illnesses, 4.8 million medical visits, 120,000 influenza-related hospitalizations, and 7,900 influenza-related deaths. In addition, immunized individuals are less likely to spread of infection to others they encounter. Think of grandchildren, who may themselves be at low (but not zero) risk of serious harm from influenza, passing an infection on to their grandparents, who by virtue of their age are high risk for serious illness including death. Note, for example, there was about a 4% mortality rate in hospitalized older men with influenza.

What Is the Risk of Influenza Vaccination?

Flu shots are safe. They usually have no adverse effects except some arm soreness, and often not even that. Uncommonly headaches, feeling achy, or fatigued, or minor fever. Occasionally local arm redness. Allergic reactions are rare, especially since major vaccines (such as Flublok and Fluzone) are recombinant vaccines and are egg-free. There are essentially no deaths from the flu vaccine with many millions of doses given annually. I personally administered close to 50,000 flu shots over my career and never encountered more than occasional sore arms or rare short-lived fever.

What Is the Risk/Benefit of Influenza Vaccination?

For influenza, there is substantial documented benefit described above, with no meaningful adverse vaccine effects. The benefit-to-risk ratio is exceedingly high. Even for a risk-averse person, the flu shot should be an easy “yes.”

Covid-19

What Is the Risk of Covid-19 Infection?

SARS-CoV-2 (the causative agent for Covid-19) is alive and well, constantly mutating, and likely with us for the indefinite future (i.e., endemic, in medical jargon). No surprise. Infections were a bit less than anticipated this summer, and we may have a more muted winter, but there still likely will be a substantial winter peak in January-February that will remind us of its presence.

Covid-19 remains a highly contagious and dangerous disease, even though we have Paxlovid as an oral antiviral therapy for adults. Primary symptoms are cough, congestion, fever, fatigue and GI problems in various combinations, which may be mild, but threatening complications including pneumonia regularly occur in older people, while myocarditis (inflammation of the heart muscle) and, in children, multisystem inflammatory syndrome (MIS-C) uncommonly occur at younger ages.

Covid-19 killed 76,000 people in the U.S. in 2023-24, about 3 times the deaths from influenza. The exact number of community infections has been much harder for the CDC to track since most testing is done at home and hospitals are no longer reporting frequently. But it is clear that Covid is much more prevalent than influenza and much more serious. The elderly are most likely to be hospitalized or die, but people of all ages, including children, continue to be sickened.

And then there is long Covid, a debilitating extended illness with prominent fatigue, mental impairment and a wide variety of symptoms, which occurs with substantial frequency (possibly 7-10%) after Covid infection in all age groups, including children. The cause is uncertain, with some evidence of persistent virus hiding in the body. The likelihood of long Covid symptoms increases with the frequency and severity of infections and we have yet to develop useful or reproducible therapy.

What Is the Benefit of Covid-19 Vaccination?

We continue to have excellent documentation that the Covid-19 vaccines, including the updated mRNA formulation for this fall, do a good job in preventing serious illness, hospitalization or death from Covid. They also reduce the likelihood of developing the long Covid syndrome. This means your life is not likely to be abruptly derailed from a random Covid-19 infection from a friend’s house party.

We all wish that the Covid vaccine, or the flu vaccine, could prevent the initiation of any symptoms of an infection, not just reduce the severity, but we are not there yet. Given a novel virus that rapidly multiplies when introduced to our body, it is a daunting task for our immune system to be capable of maximum effectiveness from the get-go.

We also know that Covid vaccines have saved millions of lives in the world and tens of millions of hospitalizations. For example. looking at 2020-2022, a Commonwealth Fund study estimated that the Covid vaccines averted over 3,000,000 U.S. deaths, 18 MM hospitalizations, and 120 MM infections. What an amazing accomplishment!

And importantly, as in influenza, people who are vaccinated are less likely to infect other people because their viral load is lower and diminishes more quickly. So again, a vaccinated grandchild is less likely to pass on a Covid infection to the grandparents, who are vastly more susceptible to severe disease and death. Covid vaccination protects your families as well as you.

What Is the Risk of Covid-19 Vaccination?

First off, we should all know that there are no microchips in the mRNA vaccines made by Pfizer and Moderna. They don’t cause infertility nor affect your DNA. They are not experimental. In fact they are amazingly innovative biotechnology that enabled us to produce effective vaccines in months rather than years, and were given to hundreds of millions of people around the world and which saved millions of lives. And they are safe. Example details are wonderfully laid out in an extensive report by the public health authorities in Ontario, Canada covering the 40 million vaccines they administered through this spring, Canadian vaccine adverse events report 2024 covid-19-aefi-report.

We now have accumulated almost 4 years of experience with widespread administration of mRNA Covid-19 vaccines. Our direct experience and the monitored data show the mRNA vaccines’ risks of significant adverse effects are very low. While the original primary vaccination schedule of two shots 3-4 weeks apart had a slightly higher risk of adverse events, both trivial and significant, current risks of any significant harm from the most recent Pfizer or Moderna Covid-19 vaccines are well less then 1 in 100,000. You can see this clearly in the table from the Canada study, where the most recent Pfizer vaccine has a 0.4 per 100,000 incidence of any serious adverse effect, and the Moderna only 0.7-1.5. Even then, most of the serious effects were inflammatory (myocarditis) and most (though not all) resolved without permanent injury.

Last, a graph from that same Canadian report shows clearly the higher frequency of low-level and serious adverse vaccine events in the first rounds of Covid vaccines, followed by a dramatic and continued reduction in the numbers in the last 18 months. We are clearly at a very low risk level with the Covid-19 mRNA vaccines.

What Is the Risk/Benefit of Covid-19 Vaccination?

Although precise numbers are hard to pin down, we can in practice make a reasonable approximation of the risk/benefit ratios of the Covid-19 vaccination with some simple arithmetic.

First, from the Canada data (and other studies) the risk of a serious but ultimately nonfatal reaction to recent Covid vaccines is about 0.5 per 100,000 administrations, or 5 per million (MM).

Second, we know that the most serious nonfatal complication of Covid-19, which affects all age groups, is long Covid, which appears to occur in about 5% (possibly more) of cases, based on multiple studies in the past 2 years.

Third, we can estimate high and low risk (and you can choose different numbers for yourself, if you want) of contracting Covid infection this year. We no longer have weekly published case data, but we all know that Covid is prevalent and one of your friends or family is always coming down with it, even if you haven’t had it yourself this year. I’d suggest the risk of infection is no less that 1 in 500 this year (corresponding to 14,000 cases of the 7,000,000 Massachusetts residents, which seems pretty low), and not likely to be higher than 1 in 75 (or 93,000 cases, which still seems a bit low.

So, for the 1/500 risk of infection, followed by 5% (1/20) chance of long Covid, your minimum risk of long Covid is about 1/10,000, or 100/MM. For the 1/75 maximum risk of infection, the 5% risk of long Covid would 1/1,500 or 667/MM.

Finally, compare the 5/MM chance of serious but nonfatal vaccine risk with a 100/MM risk (20x) of debilitating long Covid at a probably low rate of infection risk, or against 667/MM risk (133x) of long Covid risk based on a more realistic infection exposure risk.

You can certainly choose which risk you want to take yourself. But with these odds, I know what I’d do and recommend to others.

To Sum Up

Influenza

Influenza is highly contagious and can be very serious. It causes deaths in the 30,000 to 80,000 range each year in the U.S., mainly in people like your grandparents. Flu shots are effective at mitigating disease and have essentially no important adverse effects. They are usually free. National, state, and local health authorities all find the benefits far outweigh any risks and recommend that everyone get the flu shot. The data are clear. I completely concur.

You should get your influenza vaccine promptly if you have not yet done so.

Covid-19

Covid-19 is now an endemic, highly contagious primarily respiratory infection with a high mortality rate especially among medically vulnerable and older populations. We now also know that approximately one person in 20 who gets Covid-19 will suffer debilitating symptoms from long Covid for months or possibly years. I personally find that reality highly worrisome. You should, too. We also don’t yet really know how to treat long Covid. However, we do have data that available Covid mRNA vaccines mitigate the seriousness of Covid infections and sharply reduce the likelihood of long Covid occurring.

The Covid immunizations themselves, which are usually free, are documented to be extremely safe and have less than a 1 in 100,000 chance of causing any serious side effects, which still tend to be transient.

National, state, and local health authorities all find the benefits of updated Covid vaccines far outweigh any personal risks of side effects and recommend that everyone except infants get the updated mRNA vaccines this fall. I completely concur. These vaccines will help protect you from long Covid and your grandparents from severe disease or even Covid-induced premature death.

You should get your updated Covid-19 vaccine promptly if you have not yet done so.