Which booster shot to get and when?

I'm still uncertain myself. My key crux at the moment is how side effects of the 2nd dose compare to side-effects of the 3rd dose.

I remember some posts that suggest the amount of people who sought medical help after the 3rd dose was concerningly higher.

While researching I found https://www.cdc.gov/mmwr/volumes/70/wr/mm7039e4.htm?s_cid=mm7039e4_w as a source and going from 0/0->2.1/1.4 (Moderna/Pfizer) indeed sounds concerning. However it seems like the 0's were only based on a total of 64/66 patients so a good part of that difference might be random noise. 

Going from 25.0/15.2 to 35.2/18.1 (Moderna/Pfizer) for "Unable to perform normal daily activities" seems like it's a concerning increase in side-effects for Moderna but not for Pfizer. 

If there's immunity against PEG build up that produces the side-effects and potentially creating something like a life-time-limit for mRNA vaccines we should see that by increased side effects.

It's been a while since the above publication so if anyone finds more data it would be great to look at it.

I'm in basically the same boat as you, 30ish adult, Pfizer regime completed in April. I too have been lazy and uninterested in side effects (knocked out for a day after second dose). And I too am exceptionally interested in hearing discussion of "should I" as well as timing/choice thoughts. So -- just throwing out my thoughts. (Caveats: I'm an econ/stat type, my last bio-ish class was in high school and I remember none of it).

Should we get boosters?

I think my basic answer is "yes". The longer answer is:

• if it will allow you to reduce other precautions: yes. Free, very low risk of complications and reduces risk of covid -- allowing precautions to relax.
• if you got covid, and have been vaxxed: don't bother.
• if you don't/can't risk compensate (have already relaxed all precautions, or will never), haven't had covid: yes, but YMMV in terms of benefits.

I haven't given any consideration to "lifetime mRNA vax limits" until your mention, I have no idea how plausible that is -- but my current belief is "20% chance that's a real issue down the line".

So take everything below as being "conditional on getting a booster at all."

Timing

I plan to try to get a booster in a few weeks. The holidays are subsequently anything in January/feb are likely to be high risk for everyone. It doesn't seem unlikely to me that in terms of picomorts or QALY risk (etc) this winter -- where we still face reasonable case counts, but effective treatment regimes are still being rolled out and assessed (for now) -- is probably the highest risk period (for covid-19) remaining. Waiting until after winter thus makes little sense to me. If it going to happen in the next 6 months, it should probably be in the next month.

Choice

I have a mild preference for a Moderna booster over a Pfizer booster. Moderna efficacy seems to have been consistently a smidge higher for everything -- likely because its a larger dose (ETA: looks like booster dose is smaller so this factor may be ignorable). This + the benefits of some variation in vaccine regime makes it seem preferable. Two points on this however:

• This is a small risk change -- not worth it if it forces you to change plans or to do something "risky" without a booster. Given the choice I would choose Moderna -- I'm not sure its worth much to search it out.
• These benefits come with some risks. I've had two doses of Pfizer, and no reactions that warranted hospitalization or the like. No guarantees here -- but switching it up does add some risk. (so does just another round of pfizer).
• "Larger moderna dose" may be a negative if you are worried about some "lifetime limit on mRNA doses".

ETA:

Wrapup

Would genuinely like to hear more debate on "should", "timing", and "choice". "Should" seems likely it will be well covered by media shortly. But "timing" and "choice" are things I doubt I'll see outside of this venue.

I have decided to get my booster of the Pfizer vaccine and am scheduled to get it on Monday, November 29, the soonest day that was acceptably convenient with regard to my concerns about side effects the next day.

Reasons for the decision were as follows. I'm fairly confident that I'm making the correct decision to get a booster very soon. I'm less confident as to whether I'm choosing the best booster, but I don't think that's likely to make a big difference.

Decision to get a booster very soon

The new Omicron variant increases my risk from covid over the time frame of the next few months. I want my booster to have a substantial effect before Omicron becomes highly prevalent in the US. This was my main motivation to act very soon. I had been tentatively planning to get a booster within the next week, but may have put it off for longer before learning about Omicron.

I learned about original antigenic sin [LW(p) · GW(p)], which makes the concerns about waiting for a vaccine specific to new variants less relevant.

The CDC reported yesterday that covid boosters have less side effects than the second shot, which reduces the credence of the hypothesis of a lifetime limit on mRNA vaccines and also reduces my short-term concern about dealing with the side effects of the booster.

Decision as to which booster to get

Since I now want to get a booster very soon, the possibility of traveling to get a booster not available in the US is no longer appealing. And the risks of traveling are greater due to Omicron as well.

Convenience -- the first place where I went to book a booster (Walgreen's near my house) only allowed me to get a booster of Pfizer since my original vaccine was Pfizer. (In reality, this may have been the biggest reason.)

Getting a booster of the same vaccine as the original is the generally accepted establishment medical advice (based on Walgreen's requirement and also my doctor's advice).

The study referenced in this comment [LW(p) · GW(p)] shows weak evidence that a Pfizer or Moderna booster after first two shots of Pfizer is more effective than a J&J booster. But Moderna might be the most effective of all.

Getting the same vaccine as I have already gotten in the past is dealing with something that's more of a known quantity to my body. It seems less likely that I would have unusual side effects with the same vaccine as compared with a new vaccine that I haven't tried yet.

Getting a booster of the same vaccine puts me in a more widely studied cohort, as noted here [LW(p) · GW(p)] which might means I'll have more information relevant to my situation going forward than if I boosted with a different vaccine.

I have some thoughts that it might be better to get a J&J booster anyway since it is less likely to hit the lifetime maximum mRNA issue, or because it might do better in stimulating other areas of the immune system besides antibody production, but that is balanced out by the reasons above.

After a bit of research, I did not find any articles about a lifetime limit on mRNA vaccines. [Edit 1 -- found an article. See section 3.2.2.1. But it's an expert opinion submitted in connection with a lawsuit] [Edit 2 and the authors are affiliated with an anti-covid-vaccination group so has a stronger likelihood of bias as compared with a journal article. So it is likely quite biased.]