A pediatrician holds a dose of the measles-mumps-rubella (MMR) vaccine at his practice in Northridge, Calif. on Jan. 29, 2015. THE CANADIAN PRESS/AP, Damian Dovarganes

Infants more vulnerable to measles than previously thought: Canadian study

Babies typically don’t receive the measles vaccine until they are 12 months old

A new study suggests infants are more vulnerable to measles infection than previously thought.

The findings debunk notions that most babies are protected for much of their first year by maternal antibodies passed on through pregnancy.

In fact, Toronto researchers from the Hospital for Sick Children and Public Health Ontario say the vast majority of 196 infants they studied were susceptible by three months of age.

And none of the infants were immune at six months.

Babies typically don’t receive the measles vaccine until they are 12 months old. That results in a wide susceptibility gap that the study’s senior author called “quite alarming.”

Shelly Bolotin, a scientist at Public Health Ontario, said the findings underscore the need for everyone to keep their immunization up-to-date to protect the most vulnerable members of the population.

“This is really troubling because measles is a serious disease, and it can be quite serious in infants,” said Bolotin, also an assistant professor at the Dalla Lana School of Public Health and the Department of laboratory medicine and pathobiology at the University of Toronto.

“It can be absolutely devastating and we need to make sure that we are protecting our most vulnerable members of our population — infants.”

The study was published online Thursday and appears in the December edition of the American Academy of Pediatrics journal, Pediatrics.

It found that 20 per cent of one-month-old infants had antibody levels below the protective threshold and 92 per cent of three-month-old babies has levels below the threshold.

Bolotin said researchers already knew infant immunity declines in the first six months of life, but they did not expect such a rapid drop.

“We were surprised to see that waning or that lack of protection start earlier,” said Bolotin, who collaborated with lead author Dr. Michelle Science, infectious disease specialist at Sick Kids and also an infection control physician at Public Health Ontario.

She said the assumption that babies are protected longer is based on studies conducted in places where measles remains prevalent. In those regions, mothers have more robust antibody levels to pass on to their child because their immunity comes through natural infection and is repeatedly boosted by continual exposure to measles.

In contrast, most Canadian women of childbearing age are immune through vaccination because Canada eliminated measles in 1998. Although vaccination rates are high here, immunization through vaccine is associated with lower antibody levels than natural infection.

READ MORE: B.C.’s measles vaccination program gains traction

Bolotin said the Toronto study is unique in measuring antibodies at each month of an infant’s life from birth to 12 months. Previous research has focused on measuring immunity levels among babies at birth or those older than six months.

A companion paper written by two other experts that also appears in Pediatrics raises the question of whether it’s time to consider changing the vaccine schedule. It concludes there’s no reason to vaccinate earlier, despite ongoing outbreaks in the United States.

Bolotin acknowledged this is a challenging question for policy makers who must weigh the risk of infection against the best time to vaccinate children, whose immunity system is still maturing.

Infants between six and 11 months who travel to regions where measles is endemic are encouraged to receive an early dose of the vaccine in addition to their regular 12-month dose, but otherwise, all provinces in Canada recommend the measles, mumps, and rubella vaccine (MMR) at 12 months of age.

The schedule for a second dose of the vaccine varies across the country.

The Pediatrics commentary suggested early vaccination may actually hinder the efficacy of a later dose, resulting in lower levels of the antibody compared with children who first get the vaccine at 12 months.

“Early vaccination may also alter response after re-vaccination, leading to lower levels of the antibody compared with children who are vaccinated for the first time during the second year of life,” they state, citing one study that looked at immunity in children aged five to 10, and another published earlier this year that looked at short- and long-term impacts on children in the Netherlands.

As of late last week, Bolotin said Canada has seen 112 cases of measles this year, the vast majority of them imported or import-related.

Measles can cause severe complications including pneumonia, encephalitis and death.

Cassandra Szklarski, The Canadian Press


Like us on Facebook and follow us on Twitter.

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Boaters asked to slow down, be respectful on regional lakes

Central Okanagan Emergency Operations Centre also reminded boaters physical distancing still applies on the water

Filming to resume safely later in June: Okanagan Film Commission

Film commissioner Jon Summerland said they want to start filming again later in June

Kelowna RCMP investigate woman’s sudden death

Criminality is not suspected at this time, according to RCMP

UPDATE: Cops still on scene hours after dump truck, cyclist collide on Harvey Avenue

The woman sustained injuries to one of her legs, according to RCMP

Kelowna RCMP Supt. Mundle transferred to Southeast District

Supt. Brent Mundle spent three and a half years as the commander of the Kelowna detachment

March dental conference key to many of B.C.’s COVID-19 cases

Early infections from China, Iran were quickly contained

Vancouver Island First Nations gather to remember woman fatally shot by police

Nuu-chah-nulth Tribal Council requests an independent investigation

Police seek help identifying person of interest in Salmon Arm arson investigation

A fire in a garage was extinguished but it is being treated as an arson.

Penticton Search and Rescue respond to six calls in less than a week

Two hikers rescued in early morning search near Greyback Lake latest in series of searches

Regional District of Kootenay Boundary rescinds all Grand Forks-area evacuation orders

Evacuation alerts for 1,136 Boundary properties remain in effect as officials monitor forecasts

MAP: Dr. Henry reveals which B.C. regions have seen most COVID-19 cases

B.C. health officials release a first look at how the novel coronavirus has reached all corners of the province

In photos: Modified, yet traditional graduation gives Penticton graduates a sense of normalcy

Students around Penticton take part in pre-recorded graduation ceremonies

Tla-o-qui-aht First Nation woman, 26, fatally shot by police in Edmundston, N.B.

Police were conducting a well-being check at the time of the incident

WATCH: Burned out car be gone thanks to Vernon dealership, ski resort

Bannister GM Vernon and SilverStar Mountain Resort team up in road cleanup

Most Read