Slower running times after Pfizer

[GrassIsRiz]

I'm posting on behalf of my cousin, who wanted to know if she was alone in this. She is 38 and a keen runner. After her first Pfizer jab, she felt quite fatigued for a couple of weeks and then recovered. She had her second a month ago, immediately felt very tired again and this is still persisting now. But the thing she really is wondering about is her running times. She doesn't want to go to the doctor for it as she says it must be very small fry, and the fact she can still go running has to mean she's basically ok in the grand scheme of things. She has consistently run 5k in under 25 minutes right up to the point she had the jabs. Since she had her second, though, she hasn't done a single run under 30 minutes. She just feels much slower and more tired. Has anyone else experienced this?

Runner here!
To add to the anecdotes, I noticed no change after my first vaccine but after my second I had three days where I couldn't run at all due to flu like symptoms, then my first run back was 2 minutes per mile slower than normal (I'm a 22 minute 5ker and normally do my easy runs at 9-10 minutes per mile, on this run I could not go faster than 12 minutes per mile).

Over the course of a week it progressively improved and I'm now broadly back to normal, maybe a little slower but I have a lot of cumulative fatigue from marathon training anyway so difficult to separate that out from the vaccine effect.

It would seem to make sense that the immune response to the vaccine could impact running times in the short term while the body makes antibodies etc but should not be having an impact over the longer term, I would definitely advise going to the GP. Could be coincidental timing with the vaccine and caused by an unrelated issue which would be picked up by blood tests etc, or could be vaccine related, or could be in her head because she's worrying about feeling fatigued etc.

I was running more slowly for a couple of weeks after my COVID jab (AZ). I was the same after my flu jab. I guess the body's systems are prioritising the immune response. There's no harm getting checked out though.

I can't believe the poster above doesn't think 25 minutes is a good 5k time for a female amateur runner in her 30s. Take a look at park run results. I think the fastest woman (out of around 200 runners) at mine this week did 22/23 minutes. Most were about 10 mins slower than that.

25 min is a reasonable time but the "issue" is that this runner can now only do 30min, which is slow for a trained 5k runner and a big difference from before.

I think if she was "ill" after the vaccination then it will take some time to get back. It took me 8 weeks for my VO2 max to get back to normal after I had a relatively mild dose of Covid and I guess that's what you've had if you get side effects after the vaccine.

Actually my running performance has dropped over the last few weeks since I had the Pfizer vaccines, but TBH I've been putting that down to the humidity.

If she's otherwise well, I can't see any GP being concerned that she can "only" run 30 min.

It's definitely not lost fitness through lack of practice as she's basically kept up the same routine

The same routine, but going slower is reduced fitness, removing intensity removes training load, so she could have reduced load. However the drop is significant (although hot and humid weather slows too, and we've had that too)

There are certainly many women in 30's who can run 25 minute 5kms off little or no training, it's not something only accessible to the well trained or professional, but it's also a great time for many.

I am not a runner but have felt tired and sluggish for weeks after my second jab (AZ) .

Thank you again to everyone who's commented.

Reading this thread, I'm going to push her to go to the doctor.

She has had consistent times (always below 25 mins, sometimes as low as 23) through all kinds of times over the last decade, and this is a completely new and sudden thing. Before this year, she's had bugs, stopped running for a couple of months, etc etc., and never had a time increase before, so I do think something slightly weird is going on.

Thanks again.