Over the past two decades, the annual number of tick-borne disease cases in the U.S. has more than doubled. Each year, the population of people in the country who are infected by tick-borne diseases is thought to be 490,000.
Causes for the increase
Experts point to a resurgence of forests that were previously diminished, as well as a surge in the number of white-tailed deer, which are a favorite tick host. The consequence is an increase in the tick population and a resultant increase in human exposure to these diseases. A rise in heat and humidity related to climate create conditions that permit ticks to live in a greater number of locations and for increased spans of time. Finally, the development and availability of more accurate disease monitoring and documentation reporting systems have improved scientists’ ability to track incidents of tick-borne illnesses.
Symptoms of tick-borne diseases
In the U.S., there are an estimated 80-90 species of ticks. Ninety-seven percent of tick-borne diseases originate with one specific tick species, the deer tick, also known as the black-legged tick, or Ixodes scapularis.
Common diseases that ticks carry and spread include Lyme disease, Tick-borne relapsing fever (TBRF), and Babesiosis. People infected by these diseases will likely experience symptoms such as fever, chills, body aches, fatigue, nausea and vomiting, and hemoglobinuria (pink urine resulting from ruptured red blood cells). Absent appropriate treatment, the underlying disease can cause serious, adverse health problems that may affect the body’s major organ systems.
Vaccine development is challenging
Developing a vaccine for any disease is a research-intensive, labor-intensive, years-long process that costs enormous amounts of money. In addition, the principles and data behind the vaccine must withstand intensive scientific scrutiny, and the vaccine itself must pass multiple government approval processes.
According to the GAO (U.S. Government Accountability Office), the traditional vaccine development process consists of five stages:
- Research and development
- Preclinical
- Clinical trials (Phase 1, Phase 2, Phase 3)
- Large-scale manufacturing
- FDA review and licensure
Despite the arduous process, there are some businesses and universities working on making Lyme disease vaccination a reality.
Who is working on a Lyme disease vaccine?
At Yale, researchers are developing vaccines to control Lyme disease and other tick-borne infections by impeding the ticks’ potential to feed on humans and animals. Building on previously established research showing that a host may develop greater insusceptibility to tick-borne infections after sustaining multiple tick bites, one of the Yale researchers provided evidence that a vaccine incorporating tick salivary proteins can hinder the parasitic arachnids’ feeding capability. Further evidence suggests that the presence of the proteins can enhance the probability that the human will perceive the bite, allowing the individual to remove the tick quickly and diminish the risk of infection.
A professor emeritus of epidemiology at Yale School of Public Health believes that the same mechanism could function in an oral vaccine and be added to bait that is distributed for consumption by deer. With the vaccine rendering the ticks unable to obtain nourishment from deer blood, the tick populations would diminish and with them the probability of humans contracting tick-borne diseases. The logic behind it seems sound, as baiting programs have been implemented in the U.S. and Europe to combat rabies in racoons and foxes, respectively. Similar programs have safeguarded cattle against diseases carried and spread by ticks.
Moderna has a pair of Lyme disease vaccines in development that are based on a seven-valent strategy. One of them focuses on producing antibodies targeting Borrelia burgdorferi, the cause of nearly all Lyme disease in the U.S., while the other focuses on producing antibodies targeting the four major species of Borrelia that cause disease in the U.S. and Europe.
Prophylactic approach
University of Massachusetts researchers have come up with an injection that may provide protection on a seasonal basis, and that protection would even be effective in individuals with weakened immune systems.
At MassBiologics of UMass Chan Medical School, a contract development and manufacturing organization (CDMO), researchers are developing a prophylactic injection, called “Lyme PrEP,” that provides monoclonal antibodies to the individual. This differs from the traditional approach of delivering an inactive form of the bacteria or virus into the recipient to allow the person’s body to produce the antibodies that will effectively attack the unadulterated bacteria or virus if the pathogen finds its way into the individual’s system.
During a tick bite, some of the host’s blood is drawn into the tick’s stomach. If the host has received Lyme PrEP, antibodies are brought into the stomach as well, where they deactivate an essential protein on the Borrelia burgdorferi. This prevents the bacteria from escaping the tick’s viscera and entering the host’s blood.
The Lyme PrEP injection could offer protection that lasts for the entire tick season. A smaller dose could provide short-lasting protection – a month or less – to people who are going to be in an area with a large tick population but only for a short period of time, such as for vacation or work-related travel.
In bypassing the need for a person’s immune system to produce antibodies, and instead directly delivering antibodies to the person, the Lyme PrEP injection is likely to provide protection against Lyme disease to individuals, independent of their immune system’s health.
Timeframe for vaccine availability
Pfizer and Valneva have partnered to develop a vaccine called “VLA15” that could be available in 2024. Given in three doses, the vaccine works in the same fashion as MassBiologics’ Lyme PrEP injection – using antibodies to impede the bacteria while they are still contained within the tick’s intestines.
Take precautions
Until a Lyme disease vaccine is available, the best defense is a strong offense. Here are steps you can take to reduce your risk of a tick bite and possibly getting Lyme disease:
- Know where to expect ticks
- Treat clothing and gear with 0.5% permethrin
- Use EPA-registered insect repellents
- Avoid contact with ticks
- Check clothing for ticks
- Examine gear and pets for ticks
- Check your body for ticks after being outdoors
- Shower soon after being outdoors
