What Is Boostrix Vaccine? Uses, Side Effects & More

Boostrix is a booster vaccine that protects against three bacterial diseases: tetanus, diphtheria, and pertussis (whooping cough). Manufactured by GlaxoSmithKline, it belongs to a class of vaccines known as Tdap, which use reduced amounts of diphtheria and pertussis antigens compared with the childhood versions of these shots. Boostrix is approved for people aged ten and older, including pregnant individuals and older adults, and it plays a particularly important role in preventing whooping cough at a stage of life when childhood vaccine protection has faded.

What Boostrix Contains and How It Differs from Childhood Shots

Children receive a series of DTaP vaccines (capital letters for diphtheria and tetanus because the doses are higher) during infancy and early childhood. Those shots build strong initial immunity, but the protection they confer does not last forever. Boostrix uses lower quantities of diphtheria toxoid and pertussis antigens than the childhood formulation, which is why the abbreviation switches to “Tdap” with lowercase letters. The reduced-antigen approach is designed to refresh immunity without triggering the kind of strong local reactions that full-strength doses can cause in older arms that have already been primed by earlier vaccination.

The three pertussis components in Boostrix are pertussis toxin, filamentous hemagglutinin, and pertactin. These are purified proteins from the whooping cough bacterium rather than whole killed bacteria, which is what “acellular” means in the vaccine’s formal name. The tetanus and diphtheria portions are inactivated toxins (toxoids) that teach the immune system to neutralize the poisons these bacteria produce.

Why a Booster Is Needed

Protection from childhood pertussis vaccines fades considerably over time. A seroepidemiology study in Singapore found that while immunity to diphtheria remained relatively stable, immunity against pertussis waned substantially as people aged, leading researchers to recommend routine adolescent boosters to maintain protection.¹ This pattern is not unique to one country. Whooping cough outbreaks in highly vaccinated populations across the world have reinforced that childhood shots alone are not enough to keep pertussis at bay through adolescence and adulthood.

Tetanus and diphtheria boosters have been recommended every ten years for decades. Boostrix essentially replaces one of those routine tetanus-diphtheria (Td) boosters with a version that also covers pertussis. In practice, the U.S. Centers for Disease Control and Prevention recommends that everyone receive at least one dose of Tdap, ideally during adolescence, and that pregnant people get a dose during every pregnancy.

How Well Boostrix Works

Clinical trials consistently show that a single dose of Boostrix produces strong immune responses across age groups. In children, adolescents, and adults, the vaccine induced seroprotective antibody levels against diphtheria and tetanus in virtually all recipients, while seropositivity rates for pertussis antigens reached at least 90 percent across all age groups, including previously unvaccinated adolescents.² These responses held up regardless of vaccination history, meaning even people who had gone a long time without any booster still mounted a solid response.

The vaccine also performs well in populations that might be expected to respond less robustly. In adults with obstructive airway diseases such as asthma and COPD, roughly 89 percent reached seroprotective antibody levels against diphtheria and about 97 percent against tetanus one month after vaccination, with booster responses to the three pertussis antigens ranging from about 78 to 96 percent.³ These rates were consistent with what was seen in healthy comparison groups, which is reassuring for people managing chronic lung conditions.

In adults aged 55 and over, pooled data from four clinical trials confirmed that the vaccine was immunogenic in this older group as well.⁴ Separate trials in healthy adults aged 65 and older also examined the vaccine’s safety and ability to stimulate immune responses, further supporting its use in elderly populations.⁵

How Long Does Protection Last

This is one of the less settled questions. Antibody levels against pertussis toxin begin to decline within about five years after a Tdap booster in adolescents and adults, though a subsequent booster given ten years later generally produces a strong immune response and is well tolerated.⁶ The practical implication is that Tdap vaccines are highly immunogenic in the short term, but experience with these formulations is still limited enough that the optimal timing for repeat boosters remains an open question.⁷

For tetanus and diphtheria, the every-ten-year booster schedule remains the standard guidance. The pertussis component is the weak link in terms of durability. Whether future recommendations will call for more frequent pertussis boosting, or whether next-generation vaccines will produce longer-lasting immunity, is an active area of research.

Use During Pregnancy

One of the most important uses of Boostrix is during pregnancy. When a pregnant person receives Tdap, their immune system produces antibodies that cross the placenta and give the newborn a head start against whooping cough during the first few months of life, before the baby is old enough to begin their own vaccination series. This matters because whooping cough is most dangerous, and most often fatal, in very young infants.

A study of pregnant women who received Tdap found that the transplacental transfer of pertussis antibodies was remarkably efficient. Before vaccination, only about 37 percent of mothers had adequate anti-pertussis-toxin levels, but after the shot that figure rose to about 90 percent. In their newborns, roughly 95 percent had adequate antibody levels, with a transplacental transfer ratio of nearly 147 percent, meaning the babies actually had higher antibody concentrations than their mothers.⁸

Timing within pregnancy matters. Research comparing different windows of vaccination found that newborns whose mothers were immunized between 27 and 30 weeks of gestation had significantly higher cord blood antibody levels against pertussis toxin than those whose mothers were vaccinated later, at 31 to 36 weeks or beyond 36 weeks.⁹ This is why most guidelines recommend getting Tdap early in the third trimester, ideally between weeks 27 and 36, to give the body enough time to produce antibodies and transfer them before delivery.

Safety During Pregnancy and Co-administration with Flu Shots

Pregnant individuals sometimes receive Tdap and the influenza vaccine during the same visit. A study comparing women who received both vaccines at the same appointment with those who got them at separate visits found no increased risk of fever or any medically attended adverse event from getting both at once. Among women vaccinated at 20 weeks of gestation or later, there were no differences in preterm delivery, low birth weight, or small-for-gestational-age infants between the two groups.¹⁰ This is useful information for anyone worried about receiving multiple vaccines during pregnancy, and it means fewer clinic visits are needed.

Common Side Effects

Like most vaccines, Boostrix causes side effects that are overwhelmingly mild and short-lived. The most common reactions are at the injection site: redness, swelling, and pain in the arm. Fatigue, headache, and low-grade fever can also occur. A six-year post-marketing surveillance study in Korea found that about 13 percent of vaccinated subjects reported adverse events, with the vast majority being minor injection-site reactions. Six serious adverse events were identified in the study, but none were assessed as related to the vaccination.¹¹

A large disproportionality analysis of the U.S. Vaccine Adverse Event Reporting System covering a decade of reports found over 20,000 adverse event reports linked to Tdap, but about 96 percent were classified as non-serious. The most frequently flagged signals were injection-site redness and swelling. About 70 percent of all adverse events occurred within one day of vaccination.¹² Importantly, no new or unexpected safety signals emerged among older adults, and among 744 pregnancy-related reports, no unexpected maternal or fetal safety concerns were detected.

Rare Adverse Events Worth Knowing About

A few uncommon reactions have turned up in safety monitoring. In the VAERS analysis mentioned above, adolescents showed a disproportionate signal for opisthotonus, an involuntary arching of the back, though this is very rare. In non-pregnant females, disproportionate signals appeared for bursal fluid accumulation in the shoulder and brachial radiculitis, a nerve inflammation in the arm.¹² These signals did not appear in males.

Another reaction sometimes raised as a concern is the Arthus reaction, an intense localized inflammatory response that can occur in people with very high pre-existing antibody levels, particularly if they have received tetanus-containing vaccines frequently. A review of VAERS data found only 36 Arthus reports after Tdap out of 192 such reports for all vaccines combined, putting the estimated reporting rate at about 0.1 per million doses distributed. Even when researchers specifically looked at studies where people received Tdap within five years of a previous tetanus-containing vaccine, no Arthus cases turned up.¹³ For practical purposes, this reaction is extremely rare and should not deter someone from getting vaccinated on schedule.

Boostrix Versus Adacel

In the United States, there are two Tdap vaccines available for adolescents and adults: Boostrix (GlaxoSmithKline) and Adacel (Sanofi Pasteur). The two differ in the number and type of pertussis antigens they contain. Boostrix has three pertussis components, while Adacel has five. Despite this difference, head-to-head comparison in a large randomized study found similarly high seroprotection rates against diphtheria and tetanus, and Boostrix was shown to be noninferior to Adacel for these outcomes.¹⁴ In practice, the two vaccines are considered interchangeable for most purposes. Boostrix is approved from age 10 upward with no upper age limit, while Adacel was originally licensed for ages 10 through 64, though its use has been expanded. For pregnant individuals, Boostrix is the formulation that has been most widely studied and used.

Does Whooping Cough Evolve Around the Vaccine

One of the more thought-provoking developments in pertussis science is the emergence of strains that no longer produce pertactin, one of the three pertussis antigens in Boostrix. Over the past decade, more than 90 percent of circulating whooping cough strains in some U.S. states have become pertactin-deficient, and these strains carry new, independent mutations that disrupt the pertactin gene, compelling evidence of vaccine-driven evolutionary pressure.¹⁵

The reassuring news is that this evolution has not yet made the vaccines ineffective. A study from Vermont, where pertactin-deficient strains were highly prevalent, found that both DTaP and Tdap vaccine effectiveness estimates remained similar to those observed elsewhere, suggesting the vaccines still protect against clinical disease even when the circulating bacteria have dropped pertactin.¹⁶ The other antigens in the vaccine, particularly pertussis toxin and filamentous hemagglutinin, appear to carry much of the protective weight. Still, this is a situation worth watching, and it is one reason researchers are working on next-generation pertussis vaccines that might be harder for the bacterium to evade.

The Cocooning Strategy and Its Limitations

Before maternal Tdap vaccination became standard, public health authorities promoted “cocooning,” the idea that vaccinating all adults in close contact with a newborn would create a protective bubble around the infant. The concept is intuitive, but the evidence has been disappointing. A U.S. assessment found that cocooning with Tdap had no measurable effect on infant pertussis disease, a finding consistent with much of the published literature.¹⁷ A separate evaluation similarly concluded that postpartum immunization and cocooning did not reduce pertussis illness in infants under six months of age.¹⁸

The likely reason is practical: it is very difficult to actually vaccinate every adult who comes into contact with a baby, and even vaccinated adults can still carry and transmit pertussis bacteria briefly. Maternal vaccination during pregnancy, which gives the infant their own antibodies from day one, has proven to be a far more reliable approach. Cocooning is no longer emphasized as a primary strategy, though it is still considered a reasonable backup when maternal vaccination was missed.

Why Many Eligible People Still Skip the Shot

Despite strong evidence supporting Tdap vaccination, uptake remains lower than public health goals in several populations. Among pregnant women, the most common reason for not receiving Tdap was simply not knowing it was needed during every pregnancy, accounting for about 45 percent of unvaccinated women in a nationwide U.S. survey. About a third of those women believed they were already covered because they had been vaccinated in a prior pregnancy, and another 14 percent did not know the recommendation existed at all.¹⁹

A qualitative systematic review of barriers to vaccination during pregnancy identified several recurring themes: concerns about safety and effects on the baby, lack of knowledge about the vaccine’s benefits, and a low perception of disease severity.²⁰ On the flip side, the strongest facilitators were a direct recommendation from a trusted healthcare provider, easy access to the vaccine during routine prenatal visits, and clear communication about both benefits and safety. Research from other settings has confirmed that a healthcare provider’s recommendation is the single biggest motivator, and that not being oriented by a doctor to get vaccinated was one of the strongest predictors of not receiving Tdap.²¹

Cost-Effectiveness in Adults

While Tdap vaccination for pregnant individuals and adolescents is broadly regarded as highly worthwhile, the cost-effectiveness picture for routine adult boosters is more nuanced. A U.S. cost-effectiveness analysis found that vaccinating adults aged 19 to 85 carried incremental cost-effectiveness ratios ranging from about $248,000 to $900,000 per quality-adjusted life year gained, depending on age group. The lowest cost per quality-adjusted life year was in the 65-and-older cohort, followed by the youngest adults.²² These numbers are well above conventional willingness-to-pay thresholds, which means the case for routine adult Tdap vaccination rests more on population-level disease control than on individual cost savings.

An earlier modeling study using a dynamic disease transmission framework reached a more optimistic conclusion, estimating net cost savings of about $48 million from a societal perspective when vaccinating adults 65 and older, because the indirect effects of reducing disease transmission produced benefits beyond the vaccinated individual.²³ The divergence between these two analyses highlights how sensitive the economic case is to modeling assumptions, particularly the estimated rate of pertussis underreporting and the assumed vaccine effectiveness over time. Regardless of where one falls on the economic debate, the vaccine remains the best available preventive measure against pertussis in adults.