Table 3.

Second dose of COVID-19 vaccine and its effect on the menstrual cycle (N = 1606)

Variable	N	%
Have you had your second dose
Yes, and I have had a period following my second dose	1558	97.0
Yes, but I haven't yet had a period following my second do	48	3.0
Which vaccine did you get for your second dose
AstraZeneca	250	15.6
Pfizer	1326	82.6
Moderna	30	1.9
On which day of your menstrual cycle did you get your second dose (where day 1 is the first day of your period)
1–7	340	21.2
8–14	328	20.4
15–21	409	25.5
After 21	529	32.9
Q1. After receiving the second dose, your next period was
Lighter than usual	334	20.8
Heavier than usual	275	17.1
The same as usual	997	62.1
Q2. After receiving the second dose, your next period was
Earlier than usual	287	17.9
On-time	923	57.5
Later than usual	396	24.7
Q3. After receiving the second dose, the cramps you experienced in your next period was
Worse than usual	430	26.8
Less bad than usual	143	8.9
The same as usual	1033	64.3
Q4. After receiving the second dose, premenstrual syndrome) PMS you experienced in your next period was
Worse than usual	386	24.0
Less bad than usual	110	6.8
The same as usual	1110	69.1
Have you ever noticed a change in your periods after any other vaccine
No	1565	97.4
Yes, after the flu vaccine	9	0.6
Yes, after the human papillomavirus (HPV) vaccine	2	0.1
Yes, after another vaccine	30	1.9