Media release

From: Australian Academy of Science

The Australian Academy of Science, with support from the Australian Government Department of Health, is now publishing explainer videos and articles that provides credible information on COVID-19 vaccines. The latest two articles are:

Pregnancies, periods and COVID-19 vaccines: what you need to know

Can vaccines affect fertility or pregnancy? Could a vaccinated person have an impact on others around them? And what’s going on with all the stories of people noticing changes in their menstrual cycle?

COVID-19 vaccines and variants: how do they work? 

What does it mean when scientists talk about a new ‘variant’ of a virus? Why are some variants more concerning than others, and what does that mean for COVID-19 vaccines?

Pregnancies, periods and COVID-19 vaccines: what you need to know

As COVID-19 vaccines continue to be rolled out across Australia, it makes sense that people will want to share their experiences of vaccination and get a better understanding of possible side effects. More recently, those discussions have shifted to focus on whether vaccines could have any impact on reproductive health: can vaccines affect fertility or pregnancy? Could a vaccinated person have an impact on others around them? And what’s going on with all the stories of people noticing changes in their menstrual cycle?

We all want to make the best possible decisions for our health and the health of others—and especially if there’s a new baby on the way. Let’s dive into some of the discussions happening around COVID-19 vaccines, fertility and menstruation to sift through the claims and the evidence.

What is ‘shedding’?

The term ‘shedding’ has come up in some conversations around whether a vaccinated person can affect other people around them—and no, it’s got nothing to do with spending time in small backyard structures or fluffy pets getting ready for summertime.

Viral shedding occurs when someone infected with a virus starts to release viral particles from their body into the surrounding environment. This enables the virus to spread and be transmitted from one host to another and is a normal, expected process once someone is infected.

For vaccines, it’s a different story: most vaccines cannot result in shedding of any kind of infectious particles at all.

The only vaccines with any potential to shed infectious particles from one person to another are live virus vaccines, which are made using a living virus that has been weakened (or attenuated) in a laboratory. The viruses in vaccines like these have been permanently altered so they can still reproduce and stimulate an immune response, but they don’t cause disease. Examples of live virus vaccines used in Australia include the chickenpox and rotavirus vaccines. Even if a vaccinated person sheds some viral particles, it’s extremely rare to spread enough of the virus, and for it to be strong enough, to cause disease in another person.

None of the COVID-19 vaccines are live virus vaccines: there is no way they could spread the SARS-CoV-2 virus. Instead, they prompt the body to create a spike protein—the part of the virus that attaches to a host cell—which is not infectious by itself and cannot be shed out of the body. Once built, these spike proteins will linger in the body just long enough for the immune system to develop antibodies against them. The spike proteins, and the genetic instructions your cells use to build them, break down naturally.

Can COVID-19 vaccines affect fertility?

Researchers developing vaccines take a cautious approach towards pregnant people while vaccines go through clinical trials. It’s normal for guidelines for trial participants to specify that they should take steps to avoid pregnancy during the trial, and if someone does fall pregnant, they should take extra precautions and notify researchers so that they can be monitored more closely. This is a standard measure that gets put in place until clinical trials are complete to ensure vaccine safety.

Recent studies have shown there is no evidence that mRNA-based COVID-19 vaccines (such as the Pfizer vaccine) have an impact on pregnancy or fertility. A study of over 35,000 pregnant people in the US who received an mRNA vaccine showed that side effects after vaccination are similar to those experienced by non-pregnant people. The chances of serious events like miscarriage or placental abnormalities are similar for both vaccinated and unvaccinated people. This is not surprising, as there is no reason to suspect that any of the COVID-19 vaccines should have a negative effect on fertility or pregnancy outcomes.

Large studies on other vaccines have consistently reported no impact on fertility. In fact, there is strong evidence that vaccination in pregnancy protects against infection, and may even reduce incidence of stillbirth.

What about COVID-19 itself? Research into pregnant and recently pregnant women who become sick with COVID-19 shows that there is a higher risk that both the mother and their newborn could be admitted to an intensive care unit in hospital or needing life support ventilation when compared to women who have not had COVID-19. There is also a higher risk of delivering a baby prematurely. Pregnant people with other risk factors, including being overweight or more than 35 years old, or having pre-existing high blood pressure or diabetes, are also at higher risk of severe illness from COVID-19 compared to pregnant people without these conditions.

Because of the increased risks from COVID-19 during pregnancy, it is recommended that pregnant people in Australia receive the Pfizer (Comirnaty) vaccine at any stage before, during or after their pregnancy, including while breastfeeding. Some small studies have suggested that COVID-19 vaccination may also provide indirect protection to babies by transferring antibodies through the placenta or through breastmilk, although research in this area is still ongoing.

There has also been a claim that the SARS-CoV-2 spike protein has a similar structure to a protein found in the human body called syncytin-1, which plays an important role in forming the placenta during pregnancy. Some people have thought that if the immune system develops antibodies against the spike protein, those antibodies might also mistakenly attack syncytin-1 based on its supposedly similar shape, therefore harming a pregnancy. However, syncytin-1 and the SARS-CoV-2 spike protein have very different structures, so the underlying idea does not hold true.

Do COVID-19 vaccines change your menstrual cycle?

Some people have said they noticed changes in their menstrual cycle after receiving a COVID-19 vaccine: some say their period was heavier or lighter than usual, or it arrived earlier or later than expected, for example. These reports have been anecdotal so far, meaning they have not been studied in a systematic or scientific way (although some researchers are working to investigate this). However, the number of people noticing changes has raised a few questions, such as: are these kinds of menstrual changes normal after a vaccine?

None of the COVID-19 vaccines are live virus vaccines. [The SARS-CoV-2] spike protein … is not infectious by itself and cannot be shed out of the body.

Menstrual cycles can be affected by a range of different factors, such as age, medication, illness, sudden diet or exercise changes—and stress. Evidence shows that the stress of the COVID-19 pandemic itself has had an impact on people who experience menstrual disorder, with some study participants saying their symptoms are worse, the duration of their period has changed, and their anxiety levels have risen. It’s possible that pandemic-induced stress may be contributing to the changes people have noticed in their periods following vaccination, rather than being attributable to the vaccine itself. Some people may find vaccination to be a stressful event that adds to the range of factors impacting their menstrual cycle.

It’s also important not to confuse temporary menstrual changes with long-term fertility. While there is a possibility that COVID-19 vaccination might temporarily change the timing of bleeding or ovulation, this would not have impacts on the future ability to conceive or have children.

As for whether your vaccination can affect people around you? There is no scientific evidence that simply being around a vaccinated person is going to affect another person’s period. By protecting yourself with vaccination, you can help protect others from COVID-19, a disease with potentially serious consequences—that’s the biggest impact your vaccination can have on other people. Your decision to get vaccinated matters.

This article is based on scientific evidence but is not medical advice. Please speak with your doctor for advice regarding your personal circumstances and vaccines for COVID-19.

This article was produced by the Australian Academy of Science and has been reviewed by the following experts: Professor Sarah Robertson FAA FAHMS Professor, Adelaide Medical School; Professor Lois Salamonsen FAA, Head: Endometrial Remodelling Laboratory, Hudson Institute of Medical Research, Professor Beverley Vollenhoven AM, Director of Gynaecology, Monash Health.

COVID-19 vaccines and variants: how do they work?

Alpha, beta, gamma, delta: what do they mean? The letters of the Greek alphabet are used in a range of different contexts, from history and linguistics through to science and mathematics, but they are also used to describe something that increasingly makes news headlines: new variants of SARS-CoV-2, the virus that causes COVID-19.

So what does it mean when scientists talk about a new ‘variant’ of a virus? Why are some variants more concerning than others, and what does that mean for COVID-19 vaccines?

How do variants arise?

A virus cannot reproduce on its own: it needs to infect a host so that reproduction can take place inside that host’s cells. Once a virus has made its way into a cell, it makes copies of its genetic material. This reproduction is performed by molecular machinery that generally does a good job at making sure every letter in the code is copied accurately. But, just as errors can happen in the machinery of a factory floor, mistakes can happen in copying the virus' genome.

SARS-CoV-2 has a genome of 29,900 RNA bases in its genetic sequence, and for one infected person there’s an estimated 1 to 100 billion copies of viral RNA made. That’s up to 2,990,000,000,000,000 RNA letters to transcribe accurately.

Coronaviruses have a basic proof-reading capability that does a ‘quality assurance’ check of any transcribed genetic material. While this gives the virus a chance to fix errors, it’s not perfect.

If a mistake makes it through the proof-reading stage, it will then be copied into the genome of all future viruses that are copied from it (unless there’s another future mutation that reverses the error).

These mistakes can often cause problems for the virus. Any error introduced that interferes with the ability of the virus to assemble properly, that prevents infection of another cell, or even breaks the machinery of replication described above, will block virus replication. As a result, that genetic change won’t be passed on to future generations—the mutant simply dies out. But if the mutation doesn’t cause a critical problem and the mutated virus survives successfully, it can become a variant.

What causes a variant to become ‘successful’?

A ‘successful’ virus is good at infecting people and being passed on. This doesn’t mean it necessarily makes people sicker.

If there is a mutation that makes it more infectious, but people don’t feel very sick, the virus may spread faster in the community as fewer people realise that they’re unwell and might not get tested or self-isolate.

All these mutations are also valuable for contact tracers to be confident that they have found all the infected people in the community.

What makes some variants worse than others?

• Increasing the severity of the illness

Infected people may be more likely to develop serious complications such as pneumonia or, in very severe cases, the virus could prove fatal. People with more severe symptoms are also likely to cough more, potentially spreading more of the virus into their surroundings.

• Changing the range of people who are infected by the virus

Current variants have mainly affected the older population, but if a variant arises that is more infectious in young children, this could further worsen the spread of the disease since members of this sector of the community either haven’t yet been exposed to the virus or have not been vaccinated.

• Becoming more efficient at infection

As an example, if a virus is more stable, it can survive for a longer time while in the air or on surfaces, increasing opportunities for infection. It can also be more infectious if it becomes more effective at targeting and infecting host cells.

• Appearing different or even completely ‘new’ to our immune system due to substantial changes

This means that even if people have already been vaccinated or exposed to the virus previously and developed protective antibodies against it, their protective immune response would not work against a new variant.

Will our vaccines still be effective?

This all depends on the variant, where the mutation has occurred, and how the vaccine works.

COVID-19 vaccines work by training the immune system to recognise the spike protein of the SARS-CoV-2 virus. Mutations that change the spike protein could result in the immune system not recognising the virus as efficiently and the vaccine reducing its efficacy.

If new variants end up substantially changing the way the virus appears to the immune system, there’s a good chance that new versions of current vaccines will need to be developed. So far, all current vaccines being used in Australia are still effective against the known variants.

Can we do anything about these variants?

Rapid genetic sequencing technologies have enabled far more detailed monitoring of changes in the virus than were possible in the past. By carefully tracking the changes across different variants, we can gain a better understanding of the geographical locations of the people carrying the virus. This helps health authorities to determine what kinds of actions will be required to limit its future spread.

The most effective and the simplest way to prevent the increase in the number of variants is to reduce the opportunity the virus has for mutation. Vaccination does this by blocking it from replicating in our cells. By decreasing the rate of infection (and therefore replication), there are less opportunities for it to mutate.

By breaking the cycle of viral infection, replication and spread, we can reduce the number of variants that develop and extend the usefulness of the immunity derived from the currently available vaccines.

The faster the global community can establish immunity to SARS-CoV-2, the easier it will be to limit the emergence and impact of new variants. It’s a race between our global public health and viral mutation—a race that vaccination can help us win.

This article is based on scientific evidence but is not medical advice. Please speak with your doctor for advice regarding your personal circumstances and vaccines for COVID-19.

This article was produced by the Australian Academy of Science. It has been reviewed by the following experts: Professor Tony Basten AO FAA FTSE, Garvan Institute of Medical Research (retired); Professor Kanta Subbarao, WHO Collaborating Centre for Reference and Research on Influenza and The Doherty Institute.