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.
MILWAUKEE (AP) — Whooping cough is at its highest level in a decade for this time of year, U.S. health officials reported Thursday.
There have been 18,506 cases of whooping cough reported so far, the Centers for Disease Control and Prevention said. That’s the most at this point in the year since 2014, when cases topped 21,800.
The increase is not unexpected — whooping cough peaks every three to five years, health experts said. And the numbers indicate a return to levels before the coronavirus pandemic, when whooping cough and other contagious illnesses plummeted.
Still, the tally has some state health officials concerned, including those in Wisconsin, where there have been about 1,000 cases so far this year, compared to a total of 51 last year.
Nationwide, CDC has reported that kindergarten vaccination rates dipped last year and vaccine exemptions are at an all-time high. Thursday, it released state figures, showing that about 86% of kindergartners in Wisconsin got the whooping cough vaccine, compared to more than 92% nationally.
Whooping cough, also called pertussis, usually starts out like a cold, with a runny nose and other common symptoms, before turning into a prolonged cough. It is treated with antibiotics. Whooping cough used to be very common until a vaccine was introduced in the 1950s, which is now part of routine childhood vaccinations. It is in a shot along with tetanus and diphtheria vaccines. The combo shot is recommended for adults every 10 years.
“They used to call it the 100-day cough because it literally lasts for 100 days,” said Joyce Knestrick, a family nurse practitioner in Wheeling, West Virginia.
Whooping cough is usually seen mostly in infants and young children, who can develop serious complications. That’s why the vaccine is recommended during pregnancy, to pass along protection to the newborn, and for those who spend a lot of time with infants.
But public health workers say outbreaks this year are hitting older kids and teens. In Pennsylvania, most outbreaks have been in middle school, high school and college settings, an official said. Nearly all the cases in Douglas County, Nebraska, are schoolkids and teens, said Justin Frederick, deputy director of the health department.
That includes his own teenage daughter.
“It’s a horrible disease. She still wakes up — after being treated with her antibiotics — in a panic because she’s coughing so much she can’t breathe,” he said.
It’s important to get tested and treated with antibiotics early, said Dr. Kris Bryant, who specializes in pediatric infectious diseases at Norton Children’s in Louisville, Kentucky. People exposed to the bacteria can also take antibiotics to stop the spread.
“Pertussis is worth preventing,” Bryant said. “The good news is that we have safe and effective vaccines.”
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AP data journalist Kasturi Pananjady contributed to this report.
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The Associated Press Health and Science Department receives support from the Robert Wood Johnson Foundation. The AP is solely responsible for all content.
How a sperm and egg fuse together has long been a mystery.
New research by scientists in Austria provides tantalizing clues, showing fertilization works like a lock and key across the animal kingdom, from fish to people.
“We discovered this mechanism that’s really fundamental across all vertebrates as far as we can tell,” said co-author Andrea Pauli at the Research Institute of Molecular Pathology in Vienna.
The team found that three proteins on the sperm join to form a sort of key that unlocks the egg, allowing the sperm to attach. Their findings, drawn from studies in zebrafish, mice, and human cells, show how this process has persisted over millions of years of evolution. Results were published Thursday in the journal Cell.
Scientists had previously known about two proteins, one on the surface of the sperm and another on the egg’s membrane. Working with international collaborators, Pauli’s lab used Google DeepMind’s artificial intelligence tool AlphaFold — whose developers were awarded a Nobel Prize earlier this month — to help them identify a new protein that allows the first molecular connection between sperm and egg. They also demonstrated how it functions in living things.
It wasn’t previously known how the proteins “worked together as a team in order to allow sperm and egg to recognize each other,” Pauli said.
Scientists still don’t know how the sperm actually gets inside the egg after it attaches and hope to delve into that next.
Eventually, Pauli said, such work could help other scientists understand infertility better or develop new birth control methods.
The work provides targets for the development of male contraceptives in particular, said David Greenstein, a genetics and cell biology expert at the University of Minnesota who was not involved in the study.
The latest study “also underscores the importance of this year’s Nobel Prize in chemistry,” he said in an email.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.
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