Moderna side effects - does reacting to shot 1 predict a rough shot 2?

March 27, 2021 3:35 PM

I had not-terrible but more severe than average side effects from the first shot of the Moderna vaccine. Does that predict that I'm also likely to have worse than average side effects from the second shot?

I have a major work project due two days after I'm scheduled for the second shot that will require both a bunch of work around that time as well as presenting it to various bigwigs on-camera for several hours. The presentation cannot be rescheduled.

I'd rather not alter from the recommended timing of the doses but if it's likely that I'll get walloped by the second one, I might look into getting it a few days early or late. I can find a bunch of information about the side effects in general but haven't seen anything (even anecdotal) that tries to correlate across both injections.

Anecdotes are welcome, links to studies are even better.

posted by Candleman to Health & Fitness (24 answers total)

I'm riding the effects of Dose 2 from Moderna right now. Had the shot at 3:15p US Eastern yesterday. I still felt good enough last evening to go for a 6-mile walk. Overnight, I started to develop body aches and a mild fever. Today I've had low grade fever and chills. The body aches are decently strong. It feels like I did 8 hours of Pilates last night. I'm just sore in pretty much every long muscle, my head, etc. My right hamstring started to cramp a little while ago but didn't go all the way.

I had a super sore arm from Dose 1, and I was really sleepy for about 36 hours, but the fever and body aches didn't happen on that one.

Many people in our community have reported worse side effects on Dose 1 than Dose 2. Of course the opposite is true for some people, like me.

If you can shift that second appointment, you might want to give it a try. If nothing else, you'll worry less about potential impacts on that bigwig meeting. I was a lot less anxious coming into the second dose, figuring after the first one that I could handle what it threw at me. But I gave myself this whole weekend to recover, and it's looking like that was wise.
posted by sockshaveholes at 3:40 PM on March 27, 2021

I had the worst side effects after Moderna #1 by far, but YMMV of course.

Are you able to at least tell them your situation and get some degree of compassion?
posted by I_Love_Bananas at 4:04 PM on March 27, 2021 [3 favorites]

Just a data point, but Mr. BlahLaLa had side effects with dose 1, but none with dose 2.
posted by BlahLaLa at 4:20 PM on March 27, 2021

I had nearly two weeks of symptoms and exhaustion after the fist Moderna shot. My husband had a couple of days of tiredness and aches. I was not looking forward to the second shot.

Got the second shot yesterday morning. We were tired and achey in the afternoon. We both took a nap after work as we didn’t have much appetite for dinner right away. I woke up a bit out of it but not bad. My husband’s symptoms have gotten worse, exhausted, aches, and low fever.

He has slept a good chunk of the afternoon today. I have been a bit tired and my arm aches, with the only other discomfort being some heartburn.
posted by Animus at 4:47 PM on March 27, 2021

Getting the booster late is okay, apparently. Early is not okay. CDC:
"If it is not feasible to adhere to the recommended interval, you may schedule the second dose up to 6 weeks (42 days) after the first dose"
posted by Don Pepino at 5:53 PM on March 27, 2021 [6 favorites]

I had slight fever after second Moderna dose but felt fine throughout. Mrs. Geek had a viral-like syndrome with cough, fever, etc. beginning 2nd day after second dose but I think it was unrelated. Mrs. Geek’s mother (age 90) had no issues.

Good luck.
posted by sudogeek at 6:27 PM on March 27, 2021

Both Moderna and Pfizer picked their second dose interval at about the earliest possible time a booster would work well--because they wanted to get people moving towards immunity at the fastest possible rate.

So I wouldn't get either one of them earlier than the recommended scheduled but if you get the booster dose a week or two--or even three or four--later, it's only going to make it more effective in the end. The downside of course is that your full immunity will kick in that much later.

This is generic info relevant to any two-dose vaccine. It has to do with how the human immune system works and the time involved for various things to happen etc. Generally speaking there is going to be an "inverted U" shape to the graph of the time interval from first to second dose and effectiveness. Three weeks is about the soonest the second dose will be effective enough, and from that point the inverted U will continue going up for several weeks at least, and then back down. So the timescale involved there is maybe 12 weeks total?

As far as I know none of the current covid vaccines has been systematically tested for different dose intervals, so you can't say anything about them with 100% fully tested confidence.
posted by flug at 9:28 PM on March 27, 2021 [5 favorites]

Epidemiologist here. There is precisely zero peer reviewed lit on this now and there won't be for some time, because the signs and symptoms you're asking about are entirely idiosyncratic and poorly understood. And I mean that in a broadly applicable immunological sense, not just as applied to the Moderna vaccine or even vaccines in general. People, for unclear reasons and via diverse overlapping mechanisms, do not report the same bodily sensations as their immune systems are engaged.

FWIW, I *do* think that feeling unwell after an initial dose is a strong predictor of a *probable* rough time after the second dose. In my case (Moderna), I worked through my post second dose blues, but I did have a fever and felt aches and the like for about two days (starting about 12 hours after injection). But I have colleagues who barely noticed, and one colleague who needed to take a day off to sleep through it.
posted by late afternoon dreaming hotel at 1:17 AM on March 28, 2021 [5 favorites]

The recommend interval isn't exact exact. It doesn't have to be a perfect 28 days just not before. There not a little immune system timer checking the calendar. I'm not sure how difficult it would be to reschedule three days out, but you should be able to. It is really unpredictable what your immune system will do, compared to everybody else's.

When i got pfizer, (as a hcw) we were given a week window in which to schedule our second dose. it was recommended that we do it at the same time for consistancy and scheduling purposes, but it was by no means required. This was before the discussions started coming out about extending the interval if necessary.
posted by AlexiaSky at 1:20 AM on March 28, 2021

My understanding from anecdata is that one Moderna dose or the other is likely to result in unpleasant side effects, but not both.

What people here have been saying around NYC is that Moderna dose 1 typically has rough side-effects for those who previously had COVID, whether symptomatic or not, but not so much dose 2; and vice-versa for those who have not had COVID.
posted by slkinsey at 5:05 AM on March 28, 2021 [1 favorite]

All I can offer is anecdote unfortunately...I did not feel great for a few days after Moderna dose 1, felt slightly out of it/feverish in addition to soreness at the injection site. I was understandably dreading dose 2 thinking it would be worse, but I luckily had no noticeable symptoms to 2nd dose, except for the same soreness days after from the shot which seemed to last longer than the first. (I definitely recommend “gently” massaging the shot location frequently and moving your arm around, seemed to help me.)

Seconding what slkinsey said above about reaction being more severe if you previously had (or likely had) COVID; I had zero reason to suspect I ever had it, which now seems likely confirmed since my reaction was mild. Other acquaintances reported pretty severe reactions to the second dose, and in my conversations with them they surmised that they might have had it before and not known. Good luck!
posted by andruwjones26 at 6:38 AM on March 28, 2021

When scheduling my second moderna shot I was told you can get 4 data before or within a couple weeks after. You can fact check that with your provider when scheduling but i think it’s possible to avoid that time period if you want
posted by domino at 7:01 AM on March 28, 2021

You have up to 6 weeks after the first dose to get the second one and still be in the recommended timeframe.
posted by raccoon409 at 7:09 AM on March 28, 2021 [1 favorite]

To all respondents who experienced aches and fever - what did you take to relieve these symptoms? Tylenol? NyQuil? Your usual flu remedy?

I keep hearing about the symptoms but nothing about what people do about them. Thank you.
posted by seawallrunner at 9:43 AM on March 28, 2021

I felt ill for three days after my first Moderna vaccine. Eliminate the stress and get your second after your presentation. There is no way to know how you'll respond to the second one.
posted by DixieBaby at 11:54 AM on March 28, 2021

One of my colleagues got a bad fever after her second shot that knocked her out starting about 8 hours after the dose and lasting a day and a half. I *think* hers was Pfizer, but they're similar enough that I don't think you can use that as a way to discard the possibility. I personally wouldn't risk it.
posted by slidell at 12:44 PM on March 28, 2021

Due to supply issues, Canada has gone to a 4 month interval between first and second dose

Partly because they believe the Phizer vaccine has a much higher first dose efficacy (92%) than previously thought

It does have some critics though.
posted by yyz at 1:35 PM on March 28, 2021

I had no reaction to Moderna 1 beyond some site tenderness. For shot 2, taken on time, I had joint tenderness and a low fever starting 24 hours after the vaccine. It resolved within 24 hours after it started.
posted by answergrape at 6:51 PM on March 28, 2021

I had a mild temp and aches a day after Moderna 1. With shot 2 I was down for the count for 2 days. High fever, body aches, flares of pain, headache. I alternated Tylenol with ibuprofen and drank a lot of water and Gatorade. I slept as much as possible. By the end of day 2 it was like it never happened.
posted by Biblio at 9:18 PM on March 28, 2021 [1 favorite]

I had fatigue and body aches after shot 1 of the Moderna vaccine, and most of my friends who reported similar had significant symptoms after dose 2 (fever, chills, etc.), so I turned down a client-facing session for the day after shot 2 based on my expectation that I would experience severe symptoms. In your shoes, I would push my second shot appointment by a few days or a week, after your deliverables are complete.

After my second dose, I ended up being very fatigued and had a low-grade fever, but I got off lightly compared to some of my friends. I'm still glad I took that day off.
posted by bedhead at 7:19 AM on March 29, 2021

I'm curious if anyone has investigated the possibility of giving a different vaccine for the second dose. I'm old enough to qualify in Canada, so I had the Pfizer shot four days ago, and didn't feel a thing. I'll likely get the booster in a couple of months. So I'm wondering if you could opt for the Pfizer vaccine for your second shot. Is this a thing?
posted by weapons-grade pandemonium at 12:06 PM on March 29, 2021

It’s not a thing. There were no clinical trials that involved using doses from different manufacturers and the FDA Emergency Use Authorization for both the Pfizer and Moderna vaccines is for a second dose using the same manufacturer.
posted by jesourie at 2:36 PM on March 29, 2021

After Moderna #1 my arm was really sore and it hurt when I moved it. No other symptoms I can recall. Moderna #2: arm started getting sore a few hours later. I woke up in the middle of the night (12 hours after the shot) with chills/sweats and likely a low grade fever. The whole next day I felt like I had the flu. A little tired, achy, couldn't get warm. My heart rate was also elevated. It only lasted 1 day for me. Seawallrunner- I took Tylenol which definitely helped me get through work that day.
posted by Nolechick11 at 6:52 PM on March 29, 2021 [1 favorite]

I had no reaction to M1. Just got M2 this afternoon. We shall see. A good friend of mine had a bad night of chills after M2.
posted by Thorzdad at 1:01 PM on March 30, 2021