Will I be immune to the stomach flu (norovirus) in the future?
Answer: Unfortunately not.
"Stomach flu" is just a nickname for viral gastroenteritis. It is not related to influenza, the real flu. Some of the viruses that cause gastroenteritis such as rotavirus and astrovirus are thought to generate partial immunity1. But for norovirus, the immunity issue is still unclear. Earlier research suggested that you will only be immune for a few months to the exact strain of virus that you had2. There are so many different strains out there that you could easily get another one anytime. After a few months, you will lose your immunity and you can get that exact same virus again. Other research suggested that norovirus infection does not generate any immunity at all3. Some newer research found that some people had antibodies that reacted to more than one strain of norovirus4. It is also thought that SOME strains of norovirus might generate more immunity than others5 . Mathematical models suggest that there MUST be more immunity to norovirus than we think6. So, the jury is still out on whether or not any significant immunity is generated after infection with norovirus. However, since there are so many different stomach bugs, trying to generate immunity to all of them would be horrible. I know several unlucky people who had the stomach flu twice in the same month. Your best bet is to try to avoid some of these viruses.
It is very important to clean with a product that actually kills norovirus when a stomach bug is in your home such as the Clorox® Hydrogen Peroxide Spray
--Annie Pryor, Ph.D.
Your observations that immunity from stomach may be partial or only limited to certain strains seems to hold true in my experience. I am a mother of 7 young children so......you can imagine we've been through the gamut when it comes to sickness. The experiences that I'm sharing are anecdotal, but still useful, and echo the experiences of others in my community with families of multiple children.
We moved to this area, Kansas, 11 years ago, and became acquainted with the stomach virus from day one! My husband and I, and our 2 children (at that time) contracted it our very first week here. For the next 7 or 8 years, it was an annual occurrence during the winter months. This pattern continued as more children were added to the family, with some caveats. But in the past few years, I've noticed 3 very interesting things:
1. Past infection makes a difference: We no longer ALL get it EVERY year (and this is without changing much in terms of prevention or cleaning routines).
2. Age helps: Those who do get it seem to experience it in MILDER forms, especially the older they are.
3. Geography makes a difference: Those who are lifelong residents often avoid it entirely or get it in a MILD form. For example, my sister-in-law has lived here all her life. Enter my brother, who moved with us and then married her. When the stomach virus goes around, he or his young son often get it. Mama never does. Our pediatrician, who has practiced here in this town for 35 years, says he never gets the stomach viruses that go around anymore, and that he faces almost daily in clinic. My mother-in-law moved up here 5 years ago and has gotten the stomach virus each time it goes around each year. This past year, it was it's mildest yet for her. Prior to moving here, she never dealt with the yearly stomach bug thing as an adult. I think she had built up an immunity in the area (different state) where she previously lived.
This suggests to me that perhaps there are ways for us to build up at least partial immunity (praise God for some good news!).
Another example that illustrates #3. Our family of 8 traveled South 2 years ago for vacation and were exposed to a stomach virus that our cousins had just gotten over. Every single one of us was struck down with the virus within days. And it was severe with constant throwing up and the runs. I think we were exposed to a new-to-use strain of stomach virus.
So my theory is that age, prior exposure and the strains themselves can affect what type of immunity (if any) we can develop to intestinal viruses.