We're learning this week that there's good news and bad news when it comes to the effectiveness of the whooping cough vaccine. Two new Pediatrics studies show we still have a lot to learn about how we protect babies and kids when it comes to pertussis.
First, the good news: traditionally we tell parents that the first shots we give during infancy aren't fully protective for infants but rather the beginning of creating immunity against the diseases they prevent. However, a study conducted by researchers at the CDC looked back at cases of infants with pertussis from 1991-2008 and they found evidence that babies who received their whooping cough shot as early as they could, at the age of 6 weeks, were less likely to be hospitalized and/or die from the infection. Wonderful news! The first evidence out there that even that first shot, when given as early as possible, helps protect very young infants who are most at risk from whooping cough (newborns and infants < 6 months). New parents can increase protection, even during outbreaks like we're having right now, by getting their babies immunized on-time and as early as possible.
The not so good (but important) news: the effectiveness of the Tdap shot given to young teens (explained more below) doesn't always provide long-lasting protection and may wane significantly in the years after the 11-year-old booster dose is given. New research out found after one year, nearly 3/4 of teens are still protected from the booster, but by four years after the shot only about a 1/3 of them are.
Vaccine Changes May Be Affecting Outbreaks
2015 is seeing a large number of whooping cough cases reported in my home state of Washington. Most of these cases are in teenagers 18 years or younger. The predominance of children with the infection may be in part to a change in the whooping cough vaccine back in 1990s when we switched from a vaccine that was "whole cell" to an "acellular" vaccine. The reason for the switch was side effects. The new shot fortunately doesn't provoke as many fevers or subsequent seizures in young babies. However, every change comes with trade-offs; today's teens have never had a dose of the "whole cell" shot. And evidence out this week confirms what we've suspected: if teens have never had a dose of the old vaccine, their protection against whooping cough fades after immunization. Protection is not lost, it's just not as robust.
In the newly released study evaluating effectiveness during a 2012 epidemic in Washington State, researchers and epidemiologists found the vaccine is 73% effective one year after the 11-year-old booster and only about 34 percent effective 2-4 years after the booster is given. Thankfully those of us who did have a whole cell vaccine at some point in our life likely have longer lasting protection from these boosters. To learn more about the vaccine changes listen to this recent interview with Chas DeBolt, an epidemiologist at the Washington State Department of Health, who conducted the study.
Babies Are Better Protected
In perspective, we're still protecting the most vulnerable -- newborns and young infants. The Pediatrics study out this week shows the very first dose of the pertussis vaccine, given to infants at six weeks of age (DTaP), is protective against severe pneumonia, hospitalization and death. This means these young babies previously thought to be solely reliant on parents and family members for cocooned protection are better protected than we knew! This is wonderful news for parents as pertussis can cause severe respiratory distress, pauses in breathing and rarely can cause infants to stop breathing. Thankfully this data can help parents feel even better about ways they are protecting their immunized babes.
Who Needs To Be Immunized?
The realization of whooping cough shot's fading effectiveness in teens doesn't change the fact that vaccination is still the best line of defense against whooping cough. While I encourage everyone to make sure they're up to date with their immunizations, the following groups in particular need to be protected for both their own health and the health of those closest to them.
Pregnant women! In every pregnancy moms should be given the Tdap during their third trimester. We want their own immune system primed prior to delivering a baby who is at greatest risk. Moms should get this at least two weeks before delivery.
All babies at 6-8 weeks of age. No reason to wait on the first set of shots, typically called the "two-month immunizations." They can all be given as early as 6 weeks. If you're living in an area where there are whooping cough outbreaks, get your newborn into their provider's office at six weeks. Protection against serious side-effects in the rare case that they are exposed to whooping cough is worth being totally organized about this!
Children and teens. Infants, toddlers and children get the DTaP vaccine also at 4, 6, and 15 months of age. Keep doing this! Children get a DTaP booster before Kindergarten at age 4 and children get it at age 10 or 11 years. No reason to wait!
Adults, dads and grandparents who will be around a new baby also need protection. Moms tend to get protected and often in the chaos of expecting a new baby some other family members forget. Cocooning your baby is still POWERFUL. Every layer of protection you can surround an infant with is an opportunity to keep them healthy -- get any house guests up-to-date!