Do COVID vaccines prevent transmission of the virus?

It has long been established that COVID-19 vaccines reduce the risk of serious illness and hospitalisation. But there has until recently been a question mark over whether they reduce transmission of the virus.

It is an important question and one around which public health policies have been built. The United Kingdom, for example, has mandated COVID vaccines for all social care staff to protect the vulnerable people they care for; they are set to do the same for NHS staff. And in Italy, from October 15, workers will have to show proof of vaccination, a negative COVID test or recovery from a recent infection to their employer. Anyone unable to do this risks being suspended from work without pay. Other countries are adopting similar measures.

But do vaccines actually limit the spread of the virus?

A large study, not yet peer-reviewed, led by a team at Oxford University and looking specifically at the Delta variant has shown that both the Pfizer and AstraZeneca vaccines do indeed reduce transmission of the disease. The study looked at almost 150,000 contacts who were traced from nearly 100,000 initial cases of COVID. The initial COVID-positive cases contained a mix of vaccinated and unvaccinated people and the aim was not only to see which groups were most likely to pass on the virus, but also which of the Pfizer or AstraZeneca vaccines were most effective in reducing transmission.

Those who are vaccinated will have primed immune systems that will recognise the coronavirus far quicker and be able to rid their body of it faster than those who are unvaccinated.

The findings showed that both vaccines reduced transmission, but that the Pfizer vaccine was the most effective in doing so. The contacts of those who were fully vaccinated with the Pfizer vaccine were 65 percent less likely to test positive for COVID-19 compared with the contacts of those who were unvaccinated. The contacts of those fully vaccinated with the AstraZeneca vaccine, meanwhile, were 36 percent less likely to test positive when compared with the contacts of those who were unvaccinated.

As with previous studies, this Oxford study found that the vaccinated and unvaccinated groups had similar levels of the virus in their bodies, but those who were vaccinated were less likely to pass it on to others, suggesting that they clear the virus quicker and are more likely to have less infectious viral particles.

It is important to remember that those who are vaccinated will have primed immune systems that will recognise the coronavirus far quicker and be able to rid their body of it faster than those who are unvaccinated and whose immune system will take time to respond to the virus.

All of this is good news, but there is a fly in the ointment. The study also found that the protection the vaccines offer against transmission wanes over time.

Three months after having the AstraZeneca vaccine, those who had breakthrough infections were just as likely to spread the Delta variant as the unvaccinated. While protection against transmission decreased in people who had received the Pfizer vaccine, there was still a benefit when compared with unvaccinated people. Although this appears disheartening, the vaccines still offer good protection against serious illness.

With booster vaccines well under way in many developed nations, it is likely they too will help reduce transmission, and whether or not their protection against transmission wanes over time remains to be seen.

With an increasing wealth of data to suggest vaccinations reduce the risk of transmitting COVID-19 to those around us, we may well see more countries adopt stricter measures to encourage the unvaccinated to take up the vaccines – not just for themselves but for the wider population. The truth of the matter is that it is going to be a combination of vaccines and public health measures that will see us out of this pandemic.

Progress report: Why some people get rashes and sores on their toes

COVID-19 is a multi-system disorder, meaning that it can cause problems in almost any part of the body. One of the symptoms that has been reported is a rash that typically develops on the toes within four weeks of testing positive for the virus (PDF). Toes can appear red, inflamed and even swollen. For many, the rash is painless but for some it can be excruciating, affecting their ability to wear shoes and walk. It is more common in teenagers and children than adults.

Until recently, the cause was unknown. But now a team of scientists in France believe they have discovered why the virus can cause these unusual symptoms. By looking into 50 cases of “COVID toe” the researchers were able to show that it was caused by an overreaction of the immune system to the virus.

The immune systems of those affected by the symptom produced higher levels of antibodies which mistakenly targeted their own cells and tissues as well as the invading virus. The rash was a result of the cells lining the tiny blood vessels in the toes being targeted.

The researchers hope their findings will help pave the way for better treatments of those affected by the condition.

They also said that presentation of “COVID toe” was much rarer after vaccination.

Personal account: My niece and nephew contracted COVID-19

Three weeks ago, I got a call from my sister telling me that both my niece and nephew had tested positive for COVID-19. Aged 11 and nine respectively, both are too young to qualify for the vaccines here in the UK. My sister and her husband are fully vaccinated, so I told her that even though they may still get the virus, it is likely they would only suffer mild symptoms. Her main concern, however, was for the children; while my niece was just mildly tired and had a blocked nose, my nephew’s symptoms were more significant.

My nephew, Ben, is a well child. He is lucky not to suffer from any underlying health conditions and keeps himself fit by playing for the local football club. But he had come home from school in tears, complaining of a headache and pain in his legs. While the latter symptom dissipated, the headache continued and kept him awake at night. He became overwhelmed by fatigue and was struggling to get out of bed. This lasted for a week and was accompanied by frantic phone calls from my sister, asking me if there was anything that could alleviate his distress.

I felt rather helpless. We knew the cause of the illness; like several other children in his class, Ben had tested positive for COVID, but because his breathing remained stable and his cough was only a dry one, there was very little intervention that could be offered to him. If he presented at a hospital, he would have been sent home with advice to keep his fluid intake up and take paracetamol until things improved.

It was nearly two weeks before he began to feel better, and during that time not only was he missing school and vital education, he was also suffering. It made me think about all the children who were contracting COVID in school and for whom the illness was not a mild one.

Schools in the UK have removed all restrictions in an effort to get children’s education back on track after they missed large chunks of in-house teaching over the past 20 months. But huge swaths of children are now having to miss out further on their education because they have contracted COVID. The government appears to have thrown caution to the wind: abandoning masks for older children in England and failing to ensure air purifiers and filters are introduced to classrooms to reduce the risk of airborne transmission. Instead, they seem to be sticking with the archaic measures of hand-washing and social distancing “where possible”, and otherwise crossing their fingers and hoping for the best.

The prevailing message from public health outlets is that the vast majority of children will only get mild or even no symptoms should they contract COVID – but most children does not mean all children.

Luckily, Ben is now well and does not appear to have any long-lasting effects from the virus. But not all children are that lucky; according to national statistics, 25 children (aged under 18) died from COVID between March 2020 and February 2021 in England alone, six of whom had no underlying health conditions. There will be more who are suffering from Long COVID.

It is my opinion that to keep children in school, we must work to keep schools safe. Air filters need to be adopted to clear circulating air of the virus, mask-wearing for older children in communal indoor areas is a simple yet affective measure, and of course, where children are eligible they should be vaccinated.

Good News: EMA considers roll out of COVID-19 antiviral ‘pill’

The pharmaceutical giant Merk has announced that an antiviral pill it is developing can cut hospitalisations and deaths among people with COVID-19 by half.

The results of the study are yet to be peer reviewed but if they stand up to scrutiny, this will be the first oral antiviral pill that can be used in the treatment of those with COVID; all others have to be given by intravenous injection. This means it could potentially be used to treat infected people at home without the need for hospitalisation, thus playing a crucial role in preventing hospitals from being overwhelmed, as well as providing hope to developing countries where hospital capacity is limited.

The active drug in the pill is molnupiravir and it was so effective in a phase three trial involving COVID-19-positive people at risk of severe illness that clinicians ended the trial early.

Molnupiravir started its life as a possible treatment for the Venezuelan equine encephalitis virus and was being developed at Emory University in Atlanta. But when the pandemic hit, it began being tested in animals infected with the SARS-Cov-2 virus that causes COVID-19. In these animal trials, it appeared to halt not only viral replication but also viral-onward transmission.

It is understood that the European Medicines Agency (EMA) is reviewing the data around the drug and any safety concerns before making a decision in the coming days as to whether or not to roll it out more widely.

Reader’s question: Will the COVID-19 vaccine affect my period?

Although not listed as an official side-effect, some women have reported irregularities in their menstrual cycle after getting a COVID-19 vaccine.

Trials have shown that the vaccines do not affect fertility, and unplanned pregnancies were recorded at the same rate in both vaccinated and unvaccinated groups.

The UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) uses a “yellow card” system for clinicians to report and record side-effects their patients have encountered after having the vaccines, and as of September 2021, more than 30,000 reports of period irregularities were recorded.

The fact that women who had either been vaccinated with the mRNA Pfizer and Moderna vaccines or the vector-driven AstraZeneca vaccine were reporting this potential side-effect suggests it is not the vaccines causing the menstrual irregularities but the immune response to them.

Although we are yet to uncover a direct link between immune responses triggered by these vaccines and menstrual issues, there is evidence that periods can be affected by immune system activity.

In most cases, women report any menstrual issues being resolved quickly, usually by their next cycle.

If there is a link between the vaccines and menstrual issues then it needs to be investigated urgently to prevent further vaccine hesitancy in women of childbearing age, who have been targeted with misinformation about the vaccines affecting their fertility. At the same time, clinicians need to know if they should investigate irregular vaginal bleeding for other causes or seek to reassure women if they report this symptom after having a vaccine.

In the meantime, women should report any irregular vaginal bleeding to their doctor.