Whooping Cough Resurgence Raises Questions: Booster Shot or Titer Test?

This is a highly detailed and realistic close-up of Bordetella pertussis, which causes whooping cough (pertussis), a highly contagious respiratory disease. (AI)

(Adobe Stock 958655470 by phurinee)

Whooping cough (pertussis) cases have surged, leaving many wondering if their immunity is still strong. As infection rates climb, adults and healthcare providers alike are questioning whether a titer test—used to measure antibody levels—is necessary before receiving a booster shot. However, pediatric infectious disease expert Michael Glazier, MD, cofounder and chief medical officer of Bluebird Kids Health, speaking with Infection Control Today^® (ICT^®), warns that relying on titers may not be the best strategy for protection.

The Tdap vaccine, which protects against tetanus, diphtheria, and pertussis, is recommended every 10 years for adults, but some may not realize their immunity has waned. Given the rise in cases, should you get tested first or just go ahead with the booster? In this discussion, Glazier explains why boosters are the safer, more effective choice over titer testing, particularly for adults who may unknowingly transmit pertussis to infants, the most vulnerable population.

As outbreaks continue, infection preventionists (IPs) stress the importance of staying current with vaccinations rather than waiting for titer confirmation. Read on to learn why boosters are the key to preventing severe disease, reducing transmission, and protecting those at highest risk.

ICT: Would you be better off getting a titer or just getting another booster?

MG: At the end of the day, [I recommend] booster.

In general, a titer will give you a number that, in and of itself, is a blood draw, which nobody wants. More often than not, that number will tell you you need the booster. So now you've encountered, theoretically, instead of 1 needle, you've got 2. Also, I'm not certain we know the exact right titer, as it can depend on your age. Additionally, we see similar situations with other things like Hepatitis B when we start measuring titers in adults.

The pertussis or whooping cough vaccine is tied with the tetanus vaccine, so it's a combination of tetanus, diphtheria, and pertussis. You need the tetanus shot a minimum of every 10 years. So, we're doing it at age 11 as part of that initial booster series. But then they need it again when they're with us at 21, and when they enter the adult world of medicine, then [age] 31, 41, etc.

ICT: I got a tetanus shot when I was about 43 years old. I'm overdue for another tetanus shot, but I would have received the Pertussis vaccine at the same time, right?

MG: So, yes and no. As pediatricians, we are very aware of concerns related to pertussis, so we almost always administer Tdap instead of just the tetanus or diphtheria, which is the Td. However, in adult medicine, I think there's less awareness, and they often just give the tetanus shot. This is a bit of a pet peeve of mine—why not get the pertussis component as well? It’s not an additional shot but another opportunity to boost your immune system. It's a pet peeve of mine, but why not get the pertussis component now? It's not an additional shot, and it's another opportunity to boost your immune system.

Also, if you are due for the tetanus, which it sounds like you are, because it's only good for 10 years, I would ask for the Tdap instead of just the TD because you need that tetanus component, which means you need the shot. Given the 35,000 cases, why not get the Pertussis component too? And that's selfishly as a pediatrician because you may come into contact with kids in your extended family who are young, and you don't want to be one of the agents of transmission for them,

The other part of fairness in terms of this bid, this uptick, so one, as a pediatrician, we all have PTSD over COVID-19. Everybody is separating the psychosocial aspects of that and the detriment to that. Still, it did significantly slow down the transmission of respiratory illness, so I never would have imagined in my career a period where the office was quiet because that stopped COVID-19 spread; it also stopped flu spread. It also stopped pertussis from spreading and anything else that was airborne, just the mere act of being separate, and then the act of masking. Because this is transmitted via air droplets, the act of transmission, the masks helped limit that too.

Then, the testing today is easier than it was at the beginning of my career. When I started, the state lab was the only place that did pertussis testing. It was a complicated procedure where you had to do a couple of different swabs, put them in a cuff and a couple of different containers, and then send them to the state lab. Now it's a PCR, and any big lab will do it, so there may be a little bit of better diagnosis contributing to this large uptick.

ICT: What is your recommendation for IPs and other health care workers to know and share with the coughing patients?

MG: I think the first and foremost is just awareness, like awareness that we do have this incredible number of cases, and for people in hospitals in any clinical setting to suspect it because we won't know what it is if we don't test for it. So, it starts with a high index of suspicion and testing, particularly patients who would be at high risk or place others at high risk if they were to have it and it were to be untreated.

Anybody who lives with someone like a neonate, or anybody who lives with someone with congenital heart disease or severe asthma and stuff like that, I'd rather they get tested early. And I know you don't know me. I'm generally a minimalist test everything that comes in, but I'd rather know this early because if you discover what it is, in addition to the social isolation piece, you can treat it. If you treat it early enough, it helps reduce the symptoms, but it also reduces the spread.

The caveat is that the first 3 weeks of a pertussis infection appear like a cold. It's the period in which it first incubated. It's a runny nose; it's mild congestion. It's a cough that's probably when it's most transmissible, and we're treating it as the most effective. But it's only down the road that you develop that classic cough. And I don't know if you've heard the cough…but people have such a coughing spasm, a fit, that they can't get errands, so they whoop so it's like the whooping name,

ICT: You mentioned that the early symptoms resemble a cold. If you go to the doctor, they might say, "Oh, it's just a cold" and not provide anything aside from some cough medicine or something, thinking it's just a regular cold. So, when do doctors know for sure, and when should a parent or individual seek medical attention?

MG: As for these 2 things, the doctors were fallible. We should stay up to date with community trends, and this is where the benefits of information posted by the CDC become important to gauge the level of prevalence. As a health care provider, I receive notifications about best practices that alert me to a high level of something in the community. However, as patients, we also bear responsibility for our own care. I strongly believe patients should voice their concerns because it's challenging for me as a provider to dismiss what a patient has to say.

For instance, if a patient walks in and says they read about a high case rate and expresses worry due to having asthma, I appreciate that input. It reminds me to consider testing for things like pertussis. If treated early, it may shorten the duration, but if treated late, we still recommend it. While it may not shorten the illness, it does help reduce transmission. Typically, the treatment for children is azithromycin, also known as Zithromax, which is a 5-day medication that is reasonably accessible but not commonly known in the field of esoteric medicine.

Testing early enough can lower symptoms and decrease the spread. I want to be careful with that because I tend to be a minimalist and dislike unnecessarily prescribing. I’d rather say there's a high incidence of pertussis, and you’re one of the 30 patients I'm seeing, I will want to test you, regardless of whether I wait for the test results. We owe it to the community to gather as much data as possible. It's just a nasal swab, unlike during COVID-19 when you had those brain swabs.

ICT: What are the most effective prevention strategies for parents or for even adults who aren't, who've never been vaccinated, or who may have waning immunity? What can they do?

MG: I encourage vaccination for those adults who have never been vaccinated or who have waning immunity or for any kid in a similar situation. It's about awareness.

First, is there a high prevalence in the community? That raises the question of going to the doctor sooner rather than later. Second, if my child is not immunized, I should consider that child differently from how I think of other kids in the classroom. Third, although it’s highly transmissible, it spreads through coughing and the airway transmission of respiratory droplets. Masks help, so the strategic use of masks does have a place here.