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After “COVID Vaccine Arm” from My First Shot, Do I Switch Arms?

Should we choose the opposite arm for second COVID vaccine?

Key points

  • The 8th day delayed skin reaction after the first vaccine injection doesn't occur after the second injection.
  • 44 people describe that after the second injection there is either no local skin reaction or a local reaction at day 2.
  • Use of opposite arm for 2nd vaccine did not determine a more significant skin reaction.
  • People with "COVID Vaccine Arm" after the 1st vaccine are strongly encouraged to get their second dose.

After my original post where I described my own “COVID Vaccine Arm” reaction at day 8 post first Moderna shot, my questions and the questions of most of the 396 people who wrote to me with a similar 8th-day skin reaction were:

  • Should I get the second Moderna shot in the same or opposite arm?
  • Will I get “COVID Vaccine Arm” again after the second shot?
  • If I do, will the skin reaction be less or more severe than after the first vaccine shot?

When contacting the CDC asking which arm to use for the second shot, their answer was, “Get the second vaccine shot in the opposite arm.”

But a few people didn’t want to use their opposite dominant arm for the second shot. Other people contacted me saying that they were breast cancer survivors who’d had lymph nodes removed from under one arm and were told never to get any shot in that arm.

So, the breast cancer survivor women had chosen their cancer-free arm for the first vaccine shot and had to use the same arm for the second injection. But what would happen then? The unknown was anxiety-producing.

Many people debated whether they should even get a second shot despite the CDC insisting that “COVID Vaccine Arm” was not a contraindication for the second COVID vaccine shot.

In February 2021, not being able to get any further guidance from the CDC or Moderna, I decided to ask the people with “COVID Vaccine Arm” to let me know how their second shot went, and I documented what they wrote.

Results

Forty-four people (41 women and 3 men) -ages ranging from 31 to 76- with “COVID Vaccine Arm” after the 1st Moderna shot described their reaction to the second Moderna vaccine.

Out of the 44 people who reported on their 2nd Moderna shot, 21 people (48%) said they had no arm redness at all after the second shot. Twenty-three people (52%) said they experienced the same kind of “COVID Vaccine Arm.” Still, they all said the skin redness and itchiness started much earlier, around day 2 after the second shot (instead of day 8 after the 1st shot), and resolved faster.

The rash started within 24 hours post second injection (five people), at day 2 post second injection (fourteen people), and at day 3 post second injection (four people).

Eleven people said the redness was much less than the first time, whereas the other 12 reported it was about the same. All of these symptoms resolved after a few days.

Was there a difference between people using their same arm and people using their opposite arm for the second shot?

The answer is yes; there seemed to be a slight difference.

Twenty-seven people chose to have their second Moderna shot in the opposite arm, and 17 people chose to have their second Moderna shot in the same arm as the first injection.

Out of the 27 people who chose to have the 2nd shot in the opposite arm, 11 (41%) said they had no local skin reaction, and 16 (59%) said they had repeat redness and itching the injection site. Eight people said their skin reaction was similar, whereas the other 8 said their skin reaction was milder than the one experienced after the first shot.

Out of 17 people who chose to have the 2nd shot in the same arm, 10 (59%) said they had no local skin reaction, whereas 7 (41%) said they had repeat redness and itching at the injection site. One person said the skin reaction was similar, whereas the other 6 said their skin reaction was milder than the one experienced after the first shot.

Interpretation of the results and limitations

The results seem to indicate that getting the second shot in the same arm as the first shot has less risk of getting a repeat “COVID Vaccine Arm” than getting the second shot in the opposite arm.
I say, “seem to indicate,” because due to the too-small sample of people and the fact that all those reports were based on emails (I didn’t examine any of those people), we really cannot affirm anything.

We can form the one conclusion that getting “COVID Vaccine Arm” after the 1st shot should not prevent people from getting the second shot one month after, whether people get the 2nd shot in the same or opposite arm.

Other studies

My results are comparable to Dr. Kimberly Blumenthal’s results published in the New England Journal of Medicine (letter to the editor). Dr. Blumenthal describes that only 3 out of 12 patients chose to have the second injection in the same arm: one had no skin reaction, the second one had a mild rash at day 0-1, and the third had a small area of redness on day 2 and 3.

Out of the 9 patients who chose to have the second injection in the opposite arm: one had no skin reaction, 4 had a slight rash, 1 had a large rash but smaller than after the 1st shot, and 3 had a large rash similar to the one experienced after the first vaccine shot, the median onset of the skin reaction was at day 2 (range between 1 and 3 days) after the second shot, which is similar to my numbers.

But when asked about any conclusion about which arm to use for the 2nd shot, Dr. Blumenthal said: “I suspect there is a bias here. People who use the other arm had more severe reactions—potentially even ongoing reactions at the time of shot 2, which makes them choose the other arm.” Dr. Blumenthal added that she suggests using the same arm only when there is complete resolution of the rash.

Conclusion

There is no reason to hesitate to get a second vaccine shot after “COVID Vaccine Arm.” After the second shot, many people will get no local skin reaction. In contrast, others will get a skin reaction around day 2, sooner than the first vaccine reaction, which will be milder or the same (but not more) as the skin reaction after the first shot.

Unlike other symptoms, such as fever and chills, which can worsen after the 2nd vaccine shot, the local delayed skin reaction at the injection site is usually not worse.

And after 2 vaccine shots, people will be significantly protected against COVID-19, which is vital for getting out of the pandemic.

Note: To report a new “COVID Vaccine Arm” reaction, you can contact Dr. Blumenthal at allergyresearch.massgeneral.org.

Disclaimer: This article is simply a report of what people are saying. It is not intended for any medical advice. If you need medical advice, please call your healthcare provider.

References

https://www.nejm.org/doi/full/10.1056/NEJMc2102131?query=featured_home

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