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Who knew?  A study came out way back in 2016 showing that most people still had antibodies against tetanus, or “Lockjaw” even 60 years after their last vaccination. It’s a reminder of what successful vaccination can look like. It also shows the extraordinary ability of the human immune system to acquire lifelong protection — that doesn’t happen with all diseases, but it does with things like influenza, polio, measles, and mumps, and possibly tetanus and diphtheria.

The study tested the blood of 546 people. Given the striking results the authors suggest that the need for a ten year booster should be reassessed, but six years after the study came out the CDC and the Australian government are still saying we need “ten year boosters”. Is anyone even looking at this data?

Notably, shifting to a 30 year schedule could save the US government US$280 million each year. But Big-Pharma won’t be too happy about that. It may also prevent “80–160 cases of brachial plexus neuritis” — a rare side effect.

New Study Suggests We Don’t Actually Need a Tetanus Booster Every 10 Years

by Fiona Macdonald, April 2016

We’ve all grown up knowing that we need to get a tetanus booster at least once a decade in order to be protected from the potentially fatal disease.

That strategy has been incredibly safe and successful, with these days only around 31 cases of the disease being reported annually in the US. But a new study suggests that although there’s nothing wrong with being overly cautious, we could still be protected from the disease by getting just one booster every 30 years – and save a whole lot of money in the process.

… the new research looked into how long 546 adults were actually protected against diphtheria and tetanus, and found that they contained antibodies against the diseases for up to 30 years after receiving their last booster – way longer than previously assumed.

Here’s the astonishing graph of antibody titres in people after vaccination against tetanus (below). Note the scale on the x-axis, that’s a “y”. This is not days after vaccination — it’s years! Scores above −2 log10 IU/mL are considered “protected” against tetanus (marked with a dashed line). That’s nearly everyone who was studied — all 546 people involved.

The fatality rate for real tetanus is a rather nasty 13%.  But tetanus itself is so rare, that only 3 people a year die of it in the United States. However anaphylaxis rates with the vaccine are 1.6 per million, so the practice of boosting every ten years “should be reexamined” (see that discussion below).

From the caption: “95% of the population will remain protected against tetanus for 64 years after vaccination.”

Humoral immunity to tetanus as a function of age and time after vaccination. Tetanus-specific serum antibody responses were measured in adult subjects and plotted versus age (A) or time after vaccination (B). Dotted line in each panel represents level of antibody required for protection, equivalent to 0.01 IU/mL. B, Solid blue line is the fitted regression line representing the antibody half-life decay rate, and the shaded blue region represents the upper and lower bound of 95% confidence interval (CI) for the cross-sectional antibody half-life estimation. Dashed blue line represents a 1-sided lower bound 95% CI based on a 14-year half-life and indicates when tetanus-specific antibody titers would decline to 95% seroprotection by crossing the protective threshold of 0.01 IU/mL (ie, −2 log10 IU/mL) at 72 years after vaccination. Dashed green line is based on an estimated 11-year half-life [7] and indicates that 95% of the population will remain protected against tetanus for 64 years after vaccination.

Protection against Diptheria is likewise “not too shabby”:

“…95% of the population will remain protected against diphtheria for 30 years after vaccination.”

Nearly all those samples were still above the “line of protection” even a lifetime later.

Humoral immunity to diphtheria as a function of age and time after vaccination. Diphtheria-specific serum antibody responses were measured in adult subjects and plotted versus age (A) or time after vaccination (B). Dotted line in each panel represents level of antibody required for protection, equivalent to 0.01 IU/mL. B, Solid blue line is the fitted regression line representing the antibody half-life decay rate, and the shaded blue region represents the upper and lower bound of 95% confidence interval (CI) for the antibody half-life estimation. Dashed blue line represents a 1-sided lower bound 95% CI based on a 27-year half-life and indicates when diphtheria-specific antibody titers would decline to 95% seroprotection by crossing the protective threshold of 0.01 IU/mL (i.e., −2 log10 IU/mL) at 42 years after vaccination. Dashed green line is based on an estimated 19-year half-life [7] and indicates that 95% of the population will remain protected against diphtheria for 30 years after vaccination.

There is a very sane discussion of the cost benefits of over vaccinating in the paper. Even with a very safe vaccine that has minimal side effects, there is still a cost to mass vaccination programs. Currently tetanus is given in the combined DTP vaccine (Diphtheria, Tetanus, Pertussis (whooping cough). Children get five (5!) repeat shots.

Tetanus is rare in the United States, with approximately 27 cases reported annually from 2008 to 2012 [29]. Although tetanus is highly lethal in unvaccinated patients, disease severity is sharply reduced in fully vaccinated individuals [23033]. Of 124 cases of tetanus, all 14 deaths occurred in patients who had received <3 doses of vaccine or had unknown vaccination status, whereas all 110 patients (100%) who received ≥3 doses of vaccine survived [3132]. From 2001 to 2008, the Centers for Disease Control and Prevention (CDC) identified 233 tetanus cases (29 cases per year) for an annual incidence of 0.1 case per 1 million persons [33]. The overall case-fatality rate among the vaccinated, the unvaccinated, and those with unknown vaccination history was estimated at 13.2%. This indicates that tetanus is exceedingly rare, with a mortality rate of approximately 3 deaths per year among a population of >300 million.

Diphtheria is nearly nonexistent in the United States, with no cases reported from 2008 to 2012 [29]. This indicates that it is less common than other rare reportable bacterial diseases, including tularemia, plague, cholera, or anthrax [29]. Serious adverse events after vaccination against tetanus and diphtheria are uncommon, but anaphylaxis is estimated at 1.6 cases per million doses, and brachial plexus neuropathy may occur at a rate of 5–10 cases per million doses [3]. When multiplied by an estimated 16 million doses of tetanus and diphtheria (Td) vaccine administered annually in the United States [32], severe adverse events include approximately 25 severe allergic events and 80–160 cases of brachial plexus neuritis. Because overimmunization provides a negligible increase in protection [32], this suggests that the risk-benefit ratio of a decennial adult booster vaccination schedule should be reexamined.

Food for thought. I’ve heard there may be other side effects too, and I wish I had confidence the Department of Health was collecting that data diligently.

Informed consent…

REFERENCE

Hammarlund, E. et al (2016) Durability of Vaccine-Induced Immunity Against Tetanus and Diphtheria Toxins: A Cross-sectional Analysis, Clinical Infectious Diseases.  2016 July 01; 63(1): 150.

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April 23, 2022