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Given immunity to the initial course of vaccines wanes over time, booster doses are important. As with the original doses, boosters were rightly offered first to the most vulnerable. But a third dose has been available to all adults in the UK since December 2021.
Data shows more than 90% of people in England aged over 70 have received a booster or third vaccine dose. But coverage in younger adults is much lower. For example, just over 70% of young adults aged 18–24 have had one vaccine, with only 39% having received a booster.
It’s been clear since early in the pandemic that older age and a variety of underlying medical conditions put people at much higher risk of getting very sick or dying from COVID. This contrasts sharply with otherwise healthy young people where the incidence of serious illness, hospitalization, and death has been much lower.
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1. Immunity from COVID vaccines wanes over time Some vaccines, such as the MMR vaccine (measles, mumps, and rubella), can provide lifelong protection. In contrast, the effectiveness of COVID vaccines begins to decline in the months afterward.
Immunity doesn’t simply drop off a cliff. It’s a more gradual decline, with a typical reduction of about 21% in protection against infection and 10% against severe disease in the six months after vaccination.
Although the decline in immunity can be more pronounced in the elderly and those with weakened immune systems, all age groups are affected. And any notable reduction in immunity will provide opportunities for increased virus transmission, and ultimately be reflected in an increased incidence of serious illness, hospitalisation, and death.
Fortunately, protection can be effectively restored after a booster with an mRNA vaccine.
2. Protecting other people Vaccination doesn’t only protect the person being vaccinated. COVID vaccination also indirectly protects the population as a whole by reducing the onward spread of the disease.
Many young adults live in households with or meet regularly with, elderly or clinically vulnerable relatives or friends. They might have partners who are pregnant. People who are not fully vaccinated have a higher likelihood of being infected with COVID and passing it on to their close contacts.
This is clearly illustrated in Israeli research which found that children in households with two vaccinated parents were much less likely to catch COVID.
3. Reducing the impact of long COVID Many people of all ages continue to report symptoms of COVID for months after the original infection, termed “long COVID”. Long COVID can be debilitating and has been reported even after relatively mild infections. It may occur in up to 30% of people who get COVID, though estimates have varied.
It remains unclear why some people are affected while others are not. But fortunately, research shows that vaccination reduces the risk of long COVID. One study suggests a reduction of about 15%, while another suggests the risk is halved. Having a booster may further reduce this risk.
Whatever the precise level of protection, given continually high numbers of COVID infections, even a 15% reduction will lead to significantly fewer long COVID cases.
4. Fewer days off work or study For young adults in employment or education, the increased protection provided by being fully vaccinated will mean fewer days off work or interruptions to education due to illness with COVID or long COVID. At a time of increasing financial pressure, for some this may mean fewer days of income lost.
5. COVID vaccines are safe Over the past two years, billions of COVID vaccine doses have been administered across the globe. COVID vaccines have proven to be very effective and, importantly, safe.
Some serious side effects were identified on very rare occasions, such as a certain type of blood clot and myocarditis (inflammation of the heart muscle). But through careful monitoring, we have been able to identify potential risk factors for these rare side effects, and determine which vaccines and doses are most appropriate for which groups.
Certain people have expressed concerns that repeated use of vaccines could weaken the immune system. This is not true. We have been administering annual flu vaccinations for decades with no evidence that this negatively affects our immune systems.
Vaccines also don’t harm fertility. On the contrary, they may well protect against the sexual dysfunction reported by some people with long COVID. They are also safe for use during pregnancy.
Indeed, the infection itself can also confer some immunity against future infection. But vaccination is a much more precise and safe way of providing this.
Preparing for what’s to come COVID infections in the UK have begun to gradually decline over the summer months. But what might happen next is uncertain. There is concern that as we approach the winter, a new variant could cause infections and hospitalizations to skyrocket, especially if it has mutations that help it to evade vaccine protection.
With this in mind, updated vaccines designed to provide broader protection against omicron, the currently dominant COVID variant, will be deployed in the UK this autumn to older and vulnerable groups now eligible for a fourth dose.
Meanwhile, younger people who haven’t yet had their initial vaccines or booster shots must come forward. Acting now will see us better prepared for future waves of infections as we enter the winter months, and help to reduce the impact the pandemic has on our health, society, and an already pressured health service.