Image by Tina Tiller
Image by Tina Tiller

ScienceNovember 20, 2021

No, vaccinated people are not ‘just as infectious’ as unvaccinated people if they get Covid

Image by Tina Tiller
Image by Tina Tiller

A vaccinated person is less likely to get Covid in the first instance, is less contagious, and is contagious for a shorter time.

Some recent studies have shown similar peak viral loads in vaccinated people compared to unvaccinated people who contract Covid. This has raised concerns for the efficacy of vaccines for preventing transmission.

How concerned should we be? Are vaccinated people just as contagious as unvaccinated? What does this mean for future plans for reopening. These studies only show a similar peak viral load, which is the highest amount of virus in the system over the course of the study. But vaccinated people clear the virus faster, with lower levels of virus overall, and have less time with very high levels of virus present.

Therefore, vaccinated people are, on average, likely to be less contagious.

Let us explain.

Similar peak viral loads

A study in medical journal The Lancet followed 602 primary close contacts of 471 people with Covid. It documented transmission and viral load in the group.

It found there were no differences in peak viral loads between vaccinated and unvaccinated individuals. It also showed only a small decrease in the number of infections in household members between vaccinated and unvaccinated people, suggesting a similar level of infectiousness.

Another unpublished pre-print, which is yet to be reviewed by other scientists, suggests a similar trend in viral load between vaccinated and unvaccinated people, as does a CDC report in the US from July which analysed outbreak data from Massachusetts.

The Massachusetts data came from a number of large public events over a two-week period in July in Barnstable County, Massachusetts. From 469 COVID cases, 346 (74%) occurred in fully vaccinated people. Viral load was similar in both vaccinated and non-vaccinated groups.

However, we shouldn’t fear this analysis too much. The data reported is an imperfect representation of the population, and the measures they used – a single swab and PCR test – don’t provide information about overall viral load over time.

What is viral load?

Viral load refers to the amount of virus present in someone’s bodily fluids at a given point in time. Scientists can measure this by looking at your blood, or more commonly in Covid, swabs of your nose and throat.

Generally, higher viral loads are thought to correspond to a more contagious individual. However, this isn’t always clear in reality. For example, some people with Covid who don’t have symptoms and have low viral loads transmit more, as they are less likely to follow social distancing, mask wearing, or to stay at home.

The evidence on how viral load relates to severity of disease is mixed. Some studies find no relationship between the amount of virus in swabs and poorer outcomes, but others find an increased death rate with increasing viral load.

Vaccinated people clear the virus quicker

The results of the Lancet study suggest similarities in terms of viral load between vaccinated and unvaccinated people. But the study doesn’t provide strong evidence that vaccines don’t work to prevent transmission through the population. While the peak load may be similar, vaccinated people are likely to have lower viral load overall, and therefore be less contagious.

Given vaccines speed the clearance of Covid from the body, vaccinated people have less opportunity to spread the virus overall. This appears to be the case even with the more infectious delta variant.

While the Lancet study specifically collected an even number of vaccinated and unvaccinated infections in order to compare them, this isn’t a true representation of the community in most countries. We know being fully vaccinated reduces the likelihood of catching Covid even if the vaccines aren’t perfect (none are) and there are breakthrough infections.

While it’s difficult to estimate the rate of breakthrough infections accurately, studies have estimated they occur in 0.2% to 4% of people. In reality, this means that for every 100 vaccinated people, somewhere between 0.2 and 4 of them would get Covid. So, while in the rare instance where a breakthrough infection occurs, there may be a similar viral load, and possibly a similar infectiousness, there remain much fewer vaccinated people getting Covid.

Importantly, while the Lancet study also showed a similar rate of household transmission between the vaccinated and unvaccinated, there are a number of other studies in different contexts showing decreased transmission through vaccinated people.

So what does it mean for us?

If you’re one of the unlucky few vaccinated people who get a breakthrough infection, it does mean you have to follow the health advice given to you. Even though you may not feel sick, you still have the capacity to spread the virus to vulnerable people around you. Though if the people in your home are also fully vaccinated, then the risk of transmission drops even further again.

More Reading

    However, a vaccinated person is less likely to get Covid in the first instance, is less contagious, and is contagious for a shorter time, resulting in significantly less spread of the virus through a highly vaccinated community.

    This, combined with the well-known ability of vaccines to keep people out of hospital and ICU, makes them the most important part of the health response in the near future. As the vaccine rollout continues, and there are fewer people without protection, the decreased rate of breakthrough infection will help ensure a future where Covid no longer dominates the news, society, and our minds.The Conversation

    This article is republished from The Conversation under a Creative Commons license. Read the original article.

    Keep going!
    Illustrations by Julie Spray
    Illustrations by Julie Spray

    ScienceNovember 19, 2021

    An update on Covid-19 for the kids of Aotearoa

    Illustrations by Julie Spray
    Illustrations by Julie Spray

    There are nearly 800,000 New Zealanders under 12 years of age. This update is for them.

    The pandemic has already lasted 18 months, which for kids, is a pretty big part of your life. You’ve worked hard at keeping a safe distance from others, doing schoolwork from home, maybe wearing masks or getting tested, and keeping your families and communities safe.

    And now, Covid-19 is in New Zealand, and you’re still waiting for the vaccines. You might feel worried about that, or bored, or tired, or not that bothered at all. There are many ways to feel.

    Sometimes adults think that if we don’t tell you things we’re protecting you. And it’s true that sometimes it’s easier not to know about hard things! Especially when, as kids, you often have less power to do anything about the hard things. But sometimes kids prefer to know about the hard things, so they can do their best to deal with them. If that’s you, then read on.

    What is happening in the Covid-19 outbreak in Aotearoa?

    In this current delta outbreak in Aotearoa, about one third of the people infected have been children and young people under age 20. So we’re hoping to get more young people vaccinated as soon as possible.

    Even though Covid-19 is in some New Zealand communities, many adults and teenagers have been vaccinated and the vaccines are protecting them. Some people who have been vaccinated have still gotten infected, but most of them are not getting very sick or needing to go to hospital. This is good news. It means that our vaccines are working and the older people you love are more safe, and they’re helping to keep you safe too. That’s because when the virus can’t spread to your family members, it also can’t spread to you.

    When will this end?

    The truth is that we are going to be dealing with Covid-19 for a long time, but some things will get easier soon. We might have to do some things to keep safe for a long time, like wear masks or scan QR codes. More people in New Zealand will be getting sick and going to hospital.

    At the moment, we’re waiting for more people to get vaccinated so that we can move about more freely. It’s looking likely that this will happen before Christmas for kids in Auckland.

    What happens when kids get Covid-19?

    Around the world, we have seen that when kids do get Covid-19, they usually don’t get very sick. It’s common for kids to not even know that they are sick because they don’t feel any different.

    Covid-19 affects children differently to older people. For most kids, getting Covid-19 is usually a bit like getting a cold. You might get a fever, a cough, a runny nose and a headache or feel sore in your muscles.

    What are the risks for kids who get Covid-19?

    We know from Australia that about one or two out of every hundred kids who get Covid-19 need to visit the hospital, but this is usually a short stay. Very occasionally, a child might become more sick and need to stay longer in hospital.

    It is very, very rare for children to die from Covid-19. So far, there have been zero children under 12 who have died from Covid-19 in Australia. So if you do get infected, chances are you will probably get better quickly.

    Sometimes children who get Covid-19 can take a while to feel better. Kids with longer lasting symptoms might have a cough, feel tired, or lose their sense of smell for a while.

    Perhaps 1 in 25 children who get Covid-19 can have symptoms that last longer than one month. Less than 1 in 50 have symptoms that last longer than two months. But even kids who have symptoms for a long time usually recover completely after a while.

    So, it seems like the things that are worst about Covid-19 for most kids aren’t how the virus itself might make you feel, but how it affects your life and family.

    Some children have said that lockdowns can be hard because families stuck at home can feel stressed and the house can be noisy. Some children have said they miss going to school and seeing friends. Some kids say it’s unfair and upsetting not being allowed to go into shops or visit the dairies.

    Being a kid in a pandemic is hard!

    Will kids be getting a vaccine?

    The good news is that a vaccine for children has been made.

    Kids in the United States who are aged 5–11 have just started being vaccinated with a vaccine from Pfizer. Tests show the vaccine is safe and working really well at protecting kids from getting sick.

    The government has already ordered enough vaccines for all the kids aged 5-11 in Aotearoa. But we don’t know when the vaccines for kids will be here. Kids in most other countries aren’t able to get vaccinated yet either.

    It’s not a bad idea for us to be patient, because the extra wait means that when it is your turn to be vaccinated, we will have even more information about how well the vaccine is working for American kids. All of this extra information will mean that you can feel really safe about it when our turn comes.

    What will the vaccine be like?

    Vaccines for kids have littler needles and smaller doses than adult vaccines because kids’ bodies are smaller. For the kid-size Pfizer vaccine, the bottles have a special orange cap so nurses can tell them apart.

    The injection should feel about the same as other vaccines you have gotten before, so it might hurt a tiny bit but then it’s over.

    What happens when people don’t want to get vaccinated?

    While you’re waiting for your vaccine, there are things we can do to keep you safe from Covid-19 infection. The best thing is for people around you to be vaccinated. The government has said that your teachers must be vaccinated to protect you, and hopefully others in your home are vaccinated as well.

    But sometimes people are afraid of getting the vaccine or feel worried about unexpected effects of the vaccine. Recently, over 6000 doctors in New Zealand signed a letter saying it’s best to get the vaccine to prevent Covid-19, because the virus can be so dangerous.

    But if someone in your house is still too worried to get the vaccine, the best thing to do is be kind to them. With kindness people sometimes feel less scared.

    And even if people in your home are not vaccinated, there are still ways you can help stay safe. You can wash your hands. You can wear a mask when you’re out and about or at school. You can ask to play outside if it’s sunny or open the windows to let fresh air in, because we know that it’s much harder for Covid-19 to spread when we’re outside or when fresh air is coming through the house.

    If you start to feel sick like you have a cold – sneezing, coughing, a runny nose or headache – then you can ask to go get a test, just in case.

    Getting tested can be uncomfortable, but it also helps protect other people around you from catching Covid-19 from you if you have it.

    What if I have more questions?

    If you would like more information about Covid-19, here are some resources that other researchers have made for kids explaining coronavirus, and about ways to keep yourself and other people safe.

    And, if you have any more worries or questions you would like us to know about, you can email us. Julie is a researcher who talks to children about health and illness, and Jin is a doctor who cares for children.

    This article was written in consultation with Lola Huata (age 7), Jessica Brockett (age 7), Alex Williams (age 6), Theo, Violet and Henry Viskovich (ages 6, 8 & 10) and Caden and Lachlan MacDonald (ages 10 & 11).

    Note to adults

    Children and young people represent a critical 20% of New Zealand’s “team of 5 million” yet we don’t typically include them in our policy briefings or media messages. We, as researchers invested in child health, know that when children are marginalised, adults can overlook or misunderstand their needs.

    When we forget children we don’t recognise their issues. Children’s issues are often different from adult concerns because children occupy a different place in society. When children are silenced, we get to avoid some hard questions, like how children understand their risk, and what children can do if an adult in their household isn’t vaccinated.

    But these are issues that children themselves are thinking about. So we can either think about them together, or leave them to worry on their own. As American Poet June Jordan said of children, “if we will hear them, they will teach us what they need.” We want to show how children can and should be routinely included in society, especially when their efforts have contributed to keeping us all safe.