Over the past month or two, many northern hemisphere countries including the US and the UK have seen a large wave of respiratory viral infections. These include RSV (respiratory syncytial virus), flu and COVID in all ages, as well as bacterial infections such as strep A in children.
Sometimes these infections can be very serious. The UK has seen a huge surge in hospital admissions during winter, putting the health service under further stress.
This had led some to question whether COVID damages our immune systems, leaving those who have been infected more vulnerable to other infectious diseases like the flu.
Another idea put forward to explain the surge in respiratory viruses is that children “missed out” on common childhood infections during the height of the pandemic, and that this has left them more vulnerable to these infections now owing to an “immunity debt”. But how credible are these explanations?
The human immune system has evolved to deal with a host of different infections. It has a variety of weapons it can deploy which work together not only to eradicate infectious agents, but also to remember them for a more rapid and tailored response upon any subsequent encounter.
Likewise, many infectious agents have developed tricks to try to evade our immune system. For example, a parasite called Schistosoma mansoni disguises itself to avoid the immune system detecting it.
SARS-CoV-2, the virus that causes COVID-19, similarly has tricks up its sleeve. Like many other viruses, it’s been shown to evade host immunity, particularly newer variants. Recent studies showed it can interfere with immune cells’ ability to detect it within cells. This is concerning, but it’s not clear that such changes impact immunity to other infections.
Short-lived changes in a person’s immune defences are normal when they’ve been exposed to an infection. Several studies have now shown that, in response to SARS-CoV-2, specialised white blood cells called lymphocytes grow in number. These lymphocytes also display changes in their features typical of cell activation, such as changes in surface proteins.
Such changes may sound dramatic to the non-expert if taken out of context (called “ascertainment bias”). But they’re normal and merely indicate that the immune system is working as it should. Research has confirmed that, for most people, the immune system regains balance following recovery.
Some exceptions
SARS-CoV-2, like many viruses, doesn’t affect everyone equally. We’ve known for some time that certain groups, including older people and those with underlying health complications such as diabetes or obesity, can be more susceptible to severe disease when they contract COVID.
This vulnerability is associated with an irregular immune response to SARS-CoV-2 that results in inflammation. Here we see, for instance, reduced numbers of lymphocytes and changes to immune cells known as phagocytes.
Still, for most of these vulnerable people, the immune system returns to normal over the next two to four months. However, a small subset of patients, particularly those who had severe COVID or have underlying medical issues, retain some changes beyond six months after infection.
The significance of these findings isn’t clear, and longer-term studies considering the impact of underlying health conditions on immune function will be needed. But for most people, there’s no evidence to suggest immune damage following a COVID infection.
For some people with underlying health conditions, immune changes appear to last longer. pikselstock/Shutterstock
So far, no data points to immune deficiency in long COVID patients. But an overactive immune response can actually cause harm, and the immune cell changes seen in long COVID patients seem consistent with a vigorous immune response. This may explain the variety of post-infection consequences and symptoms that people with long COVID face.
Immunity debt
The “immunity debt” hypothesis suggests the immune system is like a muscle requiring near-constant exposure to infectious agents to keep it functioning. So, the argument goes, a lack of exposure due to lockdowns damaged immune development, especially in children, by making our immune systems “forget” earlier knowledge. This supposedly left them more vulnerable to infections when social mixing returned to normal.
Though this idea has gained traction, there’s no immunological evidence to support it. It’s not true to say we require a constant background of infection for our immune system to work. Our immune systems are immensely robust and powerful. For example, immune memory to the 1918 influenza pandemic was still evident after 90 years.
It’s also not strictly true to say children weren’t exposed to viruses during the early pandemic. Lockdowns didn’t commence until after waves of the usual winter respiratory infections in 2019/2020, and schools in the UK reopened in autumn 2020 with variable preventive measures, so children were still exposed to infections, including COVID-19.
The cold-causing viruses didn’t completely vanish by any means. For example, there was a significant RSV outbreak in the UK in 2021.
Nonetheless, lockdowns and other protective measures probably did reduce exposure to viruses, and for some children this shifted when and at what age they were first exposed to viruses such as RSV. This, taken alongside a high background of COVID, and relatively poor COVID and flu vaccine uptake, could all be making this season particularly bad. However, a change in the timing of when people are exposed leading to a surge of infections doesn’t necessarily mean that individual immunity has been damaged.
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Our knowledge of the immune response to COVID is rapidly expanding. The most consistent findings show how well vaccines are protecting us from the very worst effects of SARS-CoV-2 and that, post-vaccination, our immune system is working exactly as it should.
However, findings of altered immune signatures in some recovered patients and those with long COVID require further investigation.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.
Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.
Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.
Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.
The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.
“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.
Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.
Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.
Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.
A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.
This report by The Canadian Press was first published Sept. 10, 2024.
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