Should you get the RSV vaccine?
The CDC isn’t sure.
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Respiratory syncytial virus (RSV) is a respiratory virus that generally affects babies and young children. It causes approximately 58,000 hospitalizations among children under five annually. It can also infect adults, though only older adults get very sick from it. RSV infection is estimated to cause about 14,000 annual deaths in U.S. adults over age 65. Influenza (the flu) causes more deaths in that age group.
This summer two vaccines were approved by the FDA to protect adults over 60 from RSV, one made by GSK and another by Pfizer. This led many of my patients to ask the very reasonable question “Should I get it?” This led me to look at the CDC recommendations, scratch my head, and reply “I’m not really sure; let me do some more reading.” Why the uncertainty? The CDC (like yours truly) is typically a vocal proponent of vaccines. Yet their guidance for the RSV vaccine is surprisingly neutral. Please indulge me and force your way through this paragraph to appreciate the magnitude of their ambivalence.
CDC recommends that adults 60 years of age and older may receive a single dose of RSV vaccine using shared clinical decision-making (SCDM). This means that health care providers and their patients should have a conversation to determine if RSV vaccination will be beneficial. This recommendation differs from routine age-based and risk-based vaccine recommendations for which the default decision is to vaccinate all persons in a specified age group or risk group. Under SCDM, there is no default. Rather, the decision whether to vaccinate a patient is individually based and informed by discussions between the patient and health care provider.
“May receive?” “No default?” This isn’t what the CDC says about tetanus, or measles, or flu vaccinations. The CDC says you should get those. “Shared clinical decision making” is code for “Ask your doctor. Your doctor will look to the CDC for guidance, but we don’t really know. So your doctor won’t know either.”
What gives? Why the shrug and sheepish grin from an institution I look to for solid advice?
The reason is that the small benefit from the vaccine and the potential harms are very hard to balance. That’s not the case for most available vaccines. A tetanus booster, for example, is extremely safe and prevents a potentially fatal wound infection. It’s a no-brainer. I get mine every decade. But let’s look at the data from the large trials of the RSV vaccines.
The GSK vaccine trial randomized 12,467 subjects to receive the vaccine and 12,499 to receive placebo. After the first RSV season, there were 7 cases of lower respiratory infections (like pneumonia) due to RSV in the vaccine group and 40 in the placebo group. That’s an 82% decrease in the rate of serious RSV infections. Great, no? Well, a little calculation reveals that 380 people need to be vaccinated to prevent one serious infection. The same calculation for the Pfizer vaccine trial shows that 770 people need to be vaccinated to prevent one serious infection.
That would be fine if the vaccines had no side effects, but of course, everything has some side effects, so the key information is how the benefits and risks balance numerically.
Most people who received both vaccines had some side effects. The most common were pain at the injection site, fatigue, muscle aches and headaches. Let’s set those aside. Those are annoying but not dangerous. If that was the only hurdle to preventing RSV pneumonia, the CDC would probably be encouraging the vaccines. In the GSK trial, vaccine reactions severe enough to prevent normal daily activities occurred in 4% of the vaccine recipients. That means that for every 25 people receiving the vaccine, one of them can’t do their daily tasks. A little more calculation shows that to prevent one case of pneumonia, fifteen people can’t do their normal daily activities. In the Pfizer trial, preventing one lower respiratory infection meant giving eight people temporarily incapacitating vaccine side effects.
Suddenly, the benefits and harms seem about equal. If you don’t know ahead of time if you’ll be the one to get pneumonia or the one to spend a day in bed with side effects, how do you decide? Obviously, pneumonia is more serious than a day in bed with side effects, but the latter is a lot more likely than preventing the former.
There are even rarer but more serious side effects that I believe weighed on the CDC’s guidance. There were 6 additional cases of atrial fibrillation in the vaccine group over the placebo group in each trial, or one case of atrial fibrillation for about every 2,500 vaccine recipients. And there were three additional cases of serious neurological complications, like encephalomyelitis and Guillain-Barré syndrome, or one for every 5,000 vaccine recipients. I know these scary complications will likely have a big effect on my patients’ decisions. But numerically, they’re very unlikely. I’m much more worried by the frequency of inability to do daily activities. We’re putting about a dozen people out of commission temporarily for every serious infection we prevent.
So should you get the vaccine? I still have no idea. The CDC reminds doctors that some patients are at higher risk of severe RSV disease, like patients with heart disease, patients who live in long-term care facilities, and patients who are very old or frail. But those populations were excluded from the vaccine trials. So we suspect that they would derive a greater benefit from being protected from RSV, but we don’t know that.
What will I advise my patients? Well, that’s fairly subjective and liable to be biased, so take this with a grain of salt. If you’re younger than 75ish and have no serious chronic medical problems, I would pass. If you’re older than 75ish or have a medical condition that would make pneumonia very dangerous (diabetes, lung disease, heart disease), I would at least consider it. The way to consider it is to balance your desire for benefit with your tolerance for risk. If you’re the sort of person who wants to benefit from every new available intervention, and you understand you might suffer some side effects, meaning, if you want to do everything you can to avoid RSV, understanding that the vaccine is likely to make you miserable, then get it. If, on the other hand, you have a less-is-more approach and would rather minimize side effects even if that means giving up some potentially beneficial interventions, skip it.
And whatever you decide, please get a flu shot!
Learn more:
What to Know About the New R.S.V. Immunizations (New York Times)
Respiratory Syncytial Virus (RSV) Immunizations (Centers for Disease Control and Prevention)
Respiratory Syncytial Virus (RSV) (National Institute of Allergy and Infectious Diseases)
Respiratory Syncytial Virus Prefusion F Protein Vaccine in Older Adults (GSK vaccine trial) (New England Journal of Medicine, by subscription only)
Efficacy and Safety of a Bivalent RSV Prefusion F Vaccine in Older Adults (Pfizer vaccine trial) (New England Journal of Medicine, by subscription only)