While the health officials have said that just because you don't have a strong reaction that does not mean that you are not protected but they have also said those that do have a strong reaction tend to have better protection and it means their immune system is stronger than someone that didn't.
This was particularly true when talking about seniors vs those in their 20's/30's.
If you're talking about immunocompromised well yeah their immune system is not up to snuff (for whatever reason it is).
The public health officials have not really used the wording "strong reaction" at least in the way you're talking about to my knowledge. When they've spoken in article after article, press conference after press conference is to reassure those who did not receive side effects that it doesn't mean the vaccine didn't work on you.
Your comment was you didn't understand why people were afraid of to feel sick because by getting strong side effects you were saying you get better protection. To my knowledge I've not heard anything that you get
better protection just by getting strong side effects. Protection is determined by t-cells, b-cells, antibodies, etc the body's ability to recognize the enemy so to speak. Person A who does not get a fever does not mean their body did not arm itself for the enemy or in a lesser way than someone who did get a fever. Our bodies all just react differently and that includes just how it reacts to a foreign substance. To my knowledge they have looked at organ transplant recipients who basically did not get what they needed from the vaccine and aren't the best candidate for it.
If you have something in writing it would be great to look over that.
Most of what I've seen said essentially this: "Vaccine side-effects shouldn’t be taken as a measure of the effectiveness of the vaccine. Despite the varied immune response to vaccines, most people achieve immunity against the coronavirus on vaccination, regardless of the presence, absence and severity of side-effects."
Here's another comment I found: "it's not so much that sicker is better, but it just means that it's a vaccine that causes a reaction. Everybody - 95% of people who get it, almost 100% of people will get some reaction. Many of them that's an asymptomatic reaction, but others is more symptomatic. It's really just kind of a reflection of how unique each of our systems are, what other immunities we have," "You know, a lot of the antibodies cross react and we have cross reactivity so it's really a mosaic. Each of our immune systems is a mosaic composite of all that we've been through and all that we have and all we've recently been dealing with. Our individual response varies. Everybody gets gets the appropriate immune response. The symptoms vary just like they do with with pretty much every infection you could think, from all the way from asymptomatic to potentially severe. That's all a sign of our individual immune systems responding to that to that exposure."
And here's from the article I was reading about: "We talk a lot about how this is your immune system working, and [with these side effects] it's showing you that it's working. And that is true, but if a person does not experience those immune side effects or immune symptoms, that doesn't mean that their immune system isn't working." How I like to put is that there are different degrees of how loud our immune systems are. Some people's immune systems, like mine, are just really loud, obnoxious even. And then others just go along quietly, do their job and don't make a fuss. And they're doing what they're supposed to, but they're not going to make a fuss about it. So if you don't experience some of these obnoxious immune effects, don't worry about whether or not you got a good vaccine, or is it working, or is something wrong with your body. It has nothing to do with that. It's just different degrees of loudness."