Some women observe period changes after Covid-19 jab; effects temporary, vaccines are safe, say gynaecologists

• Some vaccinated women here say they have observed changes to their menstrual cycles after their Covid-19 jabs
• Their experience reflects similar reports by others around the world
• Gynaecologists said the vaccine could influence hormones that affect the menstrual cycle
• However, the effects are usually short-lived and not serious
• They gave the assurance that it is safe to get vaccinated

SINGAPORE — After Ms Joette Fong took her second Covid-19 vaccination jab in May, she noticed that her next menstruation cycle did not arrive on its scheduled date.

“The first thing I thought was that my son had a sibling, or I am going through menopause,” said the 48-year-old pet groomer.

Her period eventually arrived two weeks later but continued to be “haywire” in its start dates for the next four months. Ms Fong says that her period usually arrives every 28 to 30 days.

Ms Liang Kaixin, a 37-year-old communications specialist, observed her menstrual blood flow becoming heavier and experienced intermenstrual bleeding after getting her Covid-19 shots in June and July this year.

She also experienced irregular cycles in the months after and more severe mood swings than before.

Their observations echo reports from around the world of women experiencing menstrual disorders after getting vaccinated.

No concrete research has been conducted yet to establish the link between the two.

However, gynaecologists here gave the assurance that the impact of the vaccine on period cycles is mild and transient, and encouraged women not to put off their vaccination.

OVERSEAS REPORTS

Several countries have reported menstrual disorders accompanying vaccinations.

The United Kingdom’s Medicines and Healthcare Products Regulatory Agency, which monitors reports of suspected vaccine side effects, has logged over 30,000 reports of suspected menstrual disorder-related reactions from the Covid-19 vaccine between last December and Oct 27.

Last month, South Korea’s national health agency added menstrual disorders to its list of reportable adverse events from vaccination after petitions were raised to investigate the impact of vaccines on periods.

In Singapore, the Health Sciences Authority lists menstrual disorder as a suspected serious adverse event from the vaccination.

Serious adverse events are those that result in hospitalisation, disability or life-threatening illness or death.

However, the authority’s report, which tracks suspected adverse events from Dec 30, 2020 to Sept 30 this year, does not specify how frequently menstrual disorder was reported.

The phenomena has occurred often enough that the United States’ medical research agency, the National Institutes of Health, awarded grants of US$1.67 million (S$2.26 million) to five educational institutions in August to study the link between Covid-19 vaccination and menstrual changes.

WHAT WOMEN SAY

The five women whom TODAY interviewed said that they had observed various changes to their menstruation cycles after receiving their jabs from the national vaccination programme.

The changes include irregularities in their periods’ start date, changes to blood flow and more severe premenstrual syndrome.

However only one sought medical help as she felt “extremely worried” by the changes.

Ms Belle, a 34-year-old who works in the education sector, said that she menstruated for only three days, instead of seven usually, a month after her second vaccination dose in March.

She approached a gynaecologist for help in May after bleeding for two weeks straight that month.

Although her gynaecologist did not think that the changes were due to the vaccine, the experience has made Ms Belle fearful of taking the Covid-19 booster jab.

“I’m not taking it. I’m afraid,” she said, declining to give TODAY her full name.

The other four women said they would see through their booster jabs, although some expressed concern about the jabs’ impact on their periods.

WHAT DOCTORS SAY

Three gynaecologists said that they had patients report changes in their menstrual patterns following their vaccinations.

However, these changes were mostly mild and temporary, resolving after one to two period cycles, they said.

Gynaecologists offered several suggestions on why the vaccine seems to have an impact, noting that the actual cause had yet to be established.

Dr Chang Tou Choong of Singapore Women’s and Children’s Medical Group said that the vaccine could act like a stress factor to the body, much like how stress caused by a new job or emotional upheaval can affect or delay periods.

Dr Ng Ying Woo of Healthway Medical said that the vaccine could stimulate the immune system, influencing the hormones that drive the menstrual cycle.

Citing an article published in the British Medical Journal in September, Dr Clara Ong of Gleneagles Hospital said that immune cells could also act differently in the uterus lining after vaccination, temporarily altering how the womb lining breaks down and sheds.

She added that other vaccines, such as those for human papillomavirus, have also been linked to similar menstrual changes.

NO CAUSE FOR CONCERN

Despite these effects, gynaecologists gave the assurance that the changes to menstruation cycles are not a cause for concern and urged women to get vaccinated regardless.

Dr Ong said that the changes are “generally short-lived” and there is no evidence to show that the vaccines adversely affect fertility.

There is also no indication that the vaccines affect the effectiveness of hormonal contraception, she added.

Dr Chang said the booster jab is likely to have less of an impact on menstruation cycles compared to earlier doses.

This is because the full effect of the vaccine and its accompanying side effects are mainly felt after the second dose when the vaccine best takes effect.

Ultimately, it is safer for women, including those who are pregnant, to be protected from the effects of Covid-19 by the vaccine, said the gynaecologists.

They advised women to monitor their menstruation cycles first and seek medical help if changes to their periods after vaccination persists over several cycles.

Medicines are also available to help women manage any excessive blood flow while waiting for the effects of the vaccine to pass, said Dr Ng.