After more than three years of COVID-19, the World Health Organization (WHO) reports that over 763 million infections, and nearly seven million deaths, have been attributed to SARS-CoV-2.
COVID-19 vaccination was deemed crucial to prevent the continued spread of the disease, protect those infected from experiencing severe effects, counter the rise of new variants, and ultimately end the pandemic.
The WHO has lifted the Public Health Emergency of International Concern, but ending the ongoing threat of COVID-19 still depends on vaccination and other protective behaviours. Understanding the effectiveness of vaccines remains crucial.
Primary doses and boosters
Today, more than 5.5 billion people (72.3 per cent of the world’s population) have received at least one dose of a COVID-19 vaccine. A total of 5.09 billion people have completed a primary COVID-19 vaccination series (i.e., two doses of a two-dose vaccine or one dose of a one-dose vaccine).
At the end of 2021, several countries began offering booster doses in response to research indicating that the effectiveness of the vaccines may diminish over time, especially against the Omicron variant, which emerged in late 2021, and has become the dominant circulating variant.
People line up for COVID-19 vaccinations at a vaccine site in Québec in March 2021. THE CANADIAN PRESS/Ryan Remiorz
With this in mind, we sought to answer two questions. First, how well does the primary series of COVID-19 vaccines protect people (against infections, hospitalizations and deaths) four months or more after completing vaccination? Second, how well does the first booster dose protect people three months or more after receiving it?
Answering these questions will provide invaluable information for policymakers to make evidence-based decisions, such as the timing of administering COVID-19 vaccine booster doses.
To answer these questions we sought to identify all studies that:
Compared people who were vaccinated (either with the primary series or a booster) to people who were unvaccinated;
Followed people for at least 112 days after a primary series, or 84 days after a booster dose, and;
Looked at who got infected, was hospitalized or died due to COVID-19.
In total, we identified 68 studies that met these criteria, representing 23 countries. We then combined all the data to better understand how the vaccines’ protection changes over time. The results were published in Lancet Respiratory Medicine.
Protection against COVID-19, in general
The WHO has set standards to define whether a vaccine offers adequate protection. Specifically, vaccines should show at least 70 per cent protection against infections and 90 per cent protection against hospitalizations and deaths.
We found that the primary series offered excellent protection against hospitalizations and deaths in the short term, showing over 90 per cent protection against both outcomes within 42 days after vaccination. This protection waned over time, going below the WHO recommendation, but stayed relatively high, at around 80 per cent against hospitalizations at eight months post-vaccination, and around 85 per cent against deaths at six months post-vaccination.
The primary series of COVID-19 vaccine doses was effective in preventing infection, hospitalizations and death. THE CANADIAN PRESS/Ryan Remiorz
The primary series also offered good protection against infections in the short term (over 80 per cent within the first 42 days), but that protection fell to around 60 per cent after four months, and 50 per cent after nine months.
The initial protection of a booster dose was around 70 per cent against infections and 90 per cent against hospitalizations within the first month after vaccinations. Protection then fell to around 45 per cent against infections and to around 70 per cent against hospitalizations after four months had passed. Too little data was available to track the long-term effects against deaths.
Overall, the vaccines work at preventing infections, hospitalizations and deaths related to COVID-19, but their effectiveness does decline over time, particularly against infections. Boosters restore protection lost, but may need additional boosting over time.
Within 42 days after vaccination with the original COVID-19 vaccine formulations, the primary series only reached around 60 per cent protection against Omicron-based infections, and this dropped to around 30 per cent after five months.
The primary series’ protection against hospitalization for Omicron infections reached around 70 per cent within the first 42 days, but also dropped over time, reaching closer to 50 per cent after six months. None of these reached the levels recommended by the WHO.
The boosters did fare better in protecting against Omicron. Within the first 28 days after the booster, protection hovered close to the 70 per cent threshold against infections and 90 per cent threshold against hospitalizations recommended by the WHO.
For context, if individuals delayed the administration of the booster by six months after completing the primary series, their protection levels would be around 20 per cent against Omicron infections and around 50 per cent against hospitalizations right before receiving the booster.
Yet, booster protection also waned over time, falling to about 40 per cent against Omicron infections and 70 per cent against hospitalizations after four months post-booster. Too little data was available to comment on long-term effects against deaths.
Pfizer, left, and Moderna bivalent COVID-19 vaccines were introduced in fall 2022. (AP Photo/Steve Helber)
With Omicron, boosters are particularly needed to maintain adequate protection, but this protection also needs additional boosting as it wanes over time.
In May, the WHO recommended that new formulations of COVID-19 vaccines should target Omicron XBB variants, which are the dominant variants currently circulating.
While vaccines provide reasonable protection against COVID-19 infections, hospitalizations and deaths, their effectiveness is imperfect and wanes over time, particularly against the now-dominant Omicron variant for people vaccinated with the original vaccines.
Notably, waning is especially pronounced against infections. This means that although being vaccinated is likely to protect most people against becoming severely ill, vaccinated people are still at risk of catching the virus and transmitting it to others — some of whom will be at higher risk of severe complications from the disease.
That means measures like wearing a mask, washing one’s hands, and staying at home when sick remain essential complements to vaccination. Contrary to vaccines, these measures do not decline in effectiveness over time and are particularly well suited to protect people against infections.
Eliminating the threat of new COVID-19 infections will continue to rely heavily on a combination of vaccination and behaviours, whereas new vaccine doses will continue to protect those who are infected from severe complications like hospitalizations and deaths.
The Canadian government says it will donate up to 200,000 vaccine doses to fight the mpox outbreak in Congo and other African countries.
It says the donated doses of Imvamune will come from Canada’s existing supply and will not affect the country’s preparedness for mpox cases in this country.
Minister of Health Mark Holland says the donation “will help to protect those in the most affected regions of Africa and will help prevent further spread of the virus.”
Dr. Madhukar Pai, Canada research chair in epidemiology and global health, says although the donation is welcome, it is a very small portion of the estimated 10 million vaccine doses needed to control the outbreak.
Vaccine donations from wealthier countries have only recently started arriving in Africa, almost a month after the World Health Organization declared the mpox outbreak a public health emergency of international concern.
A few days after the declaration in August, Global Affairs Canada announced a contribution of $1 million for mpox surveillance, diagnostic tools, research and community awareness in Africa.
On Thursday, the Africa Centres for Disease Control and Prevention said mpox is still on the rise and that testing rates are “insufficient” across the continent.
Jason Kindrachuk, Canada research chair in emerging viruses at the University of Manitoba, said donating vaccines, in addition to supporting surveillance and diagnostic tests, is “massively important.”
But Kindrachuk, who has worked on the ground in Congo during the epidemic, also said that the international response to the mpox outbreak is “better late than never (but) better never late.”
“It would have been fantastic for us globally to not be in this position by having provided doses a much, much longer time prior than when we are,” he said, noting that the outbreak of clade I mpox in Congo started in early 2023.
Clade II mpox, endemic in regions of West Africa, came to the world’s attention even earlier — in 2022 — as that strain of virus spread to other countries, including Canada.
Two doses are recommended for mpox vaccination, so the donation may only benefit 100,000 people, Pai said.
Pai questioned whether Canada is contributing enough, as the federal government hasn’t said what percentage of its mpox vaccine stockpile it is donating.
“Small donations are simply not going to help end this crisis. We need to show greater solidarity and support,” he said in an email.
“That is the biggest lesson from the COVID-19 pandemic — our collective safety is tied with that of other nations.”
This report by The Canadian Press was first published Sept. 13, 2024.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
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.
