Vaccine Breakthrough Infections


You’ve had your two mRNA shots from the Pfizer or Moderna vaccines or one shot of the Johnson & Johnson vaccine. That makes you “fully vaccinated” by the government definition. Now what are your chances of getting Covid-19?

It depends – on your age, your time since vaccination, and your co-existing medical conditions such as diabetes, heart disease, chronic lung or kidney disease, or diseases that compromise your immune system. The greatest factor is age, just as it was found to be when Covid-19 first became a pandemic in 2020.

Getting Covid after vaccination is real. Though data is inconsistent, state reporting suggests there have been more than 1.89 million cases of Covid after vaccination according to The Wall Street Journal. Jon Kamp and Melanie Evans report at least 72,000 hospitalizations and 20,000 deaths among fully vaccinated people in the U.S. this year.

To be sure, the unvaccinated are still the driving force behind the pandemic numbers which have been declining in recent months. Breakthrough infections, however, are making up a growing portion because of rising numbers of vaccinated people and waning immunity among people who got their shots early on. The Journal recently studied the number of infections in the vaccinated population and found the CDC doesn’t publish a running tally on such cases. However, the Journal reviewed medical record data for a total of more than 21 million fully vaccinated people, and an array of state reports, to compile its analysis.

What they found was that people with diabetes, chronic lung and kidney disease and compromised immune systems were at much higher risk of serious outcomes from breakthrough cases. But the unvaccinated still remain those at highest risk. They are nearly five times as likely to get Covid-19 and about 29 times as likely to be hospitalized as fully vaccinated people.

The rising number of Covid infections in those who have been vaccinated led to booster shots for those over 65 years and the immunocompromised. A Mayo Clinic study estimated the efficacy of the Pfizer vaccine at only 47% and the Moderna vaccine at 75% after six to eight months. I was one of the first to get the booster shot. Recently the FDA approved booster shots for all adults. The graph below reflects this declining efficacy over time.








The risk of serious disease in the vaccinated population under 65 with no comorbidities is quite low. But for those over 65, especially with comorbidities as stated above, the risk is far higher.  Truveta, Inc., a firm that aggregates hospitals’ medical data, found among 1.7 million fully vaccinated people that those with diabetes, chronic lung disease and chronic kidney disease were about twice as likely to be hospitalized for breakthrough cases as vaccinated people with these conditions.

The likelihood of having a breakthrough infection was still low, though confirmed infections were more common for people with these illnesses. About 1.5% of roughly 110,000 people with chronic kidney disease had one, for example. (Your chances of a breakthrough case if you’re healthy is far less.) But ,Truveta found about 25% of breakthrough patients with chronic kidney disease wound up hospitalized. The likelihood of hospitalizations for people with breakthrough cases but without underlying problems was about 7.5%.

I would strongly recommend the booster shot for anyone over age 65. The recent FDA ruling that any adult can get the booster shot reflects their growing concern for breakthrough cases in all age groups.


  1. Do you think we will need another booster shot?

    Comment by Allen Higginbotham on December 9, 2021 at 9:40 pm

  2. Covid-19 is becoming an endemic, which means it will likely continue to be with us indefinitely, probably in a milder form, like influenza. It is likely we will need annual boosters for Covid much like we do for influenza.

    Comment by Robert Roberts on December 13, 2021 at 8:03 am