The need for a human vaccine against Lyme disease is a reminder that this tick-borne disease remains a major problem in New Hampshire even though our attention has been diverted by the pandemic.

“We’ve been 100% focused on COVID for two years and just now are digging out so we can look at ‘old faithfuls’ like Lyme disease,” said Patricia Tilley, director of the Division of Public Health Services for New Hampshire.

Since Lyme became widespread in New Hampshire more than a decade ago, the state has usually seen between 800 and 1,100 confirmed cases each year. Fluctuations mostly occur because of weather patterns, like when a wet summer keeps more people indoors and away from ticks.

Data from 2021 is still being crunched, Tilley said, but 2020 saw a drop in confirmed Lyme cases, to 730 from 1,107 the year before. That was the lowest figure since 2016.

The decline is a surprise since the pandemic sent people seeking outdoor recreation in record numbers where they presumably would encounter more ticks. One possible explanation is that 2020 saw health-care facilities overwhelmed by the pandemic, which could have limited how many providers were able to diagnose Lyme disease.

In any case, officials have long said that the total number of people infected with the virus that causes Lyme disease is certainly much greater than official figures.

And it’s not just Lyme. Ticks in New England are increasingly infected with viruses or bacteria that cause other diseases that are transmitted by tick bites, including babesiosis, anaplasmosis and, most recently in the area, powassan. Other diseases such as Rocky Mountain spotted fever are likely to show up here in coming years as climate change and globalization helps their spread.

“We have seen an increase in other tickborne illness,” said Tilley. However, she said this may be partly a function of increased awareness about tick-borne diseases other than Lyme, both among patients and health-care providers.

“People know when they have a tick bite and they are not feeling well, to get themselves into care – more than they did before,” she said.

Lyme disease just returned to the headlines because Pfizer and French biotech Valneva are starting to recruit people for clinical trials of a vaccine called VLA15, which protects against the major strain of Lyme found here and in Europe. They will soon be seeking 18,000 healthy people aged 5 and older from places “with high levels of endemic Lyme disease,” which definitely includes New Hampshire, to receive the vaccine or a placebo.

Participants will get three shots before “peak Lyme disease season” and then a booster dose a year later, so results will not be known until 2025 at the earliest.

The vaccine targets an outer surface protein of the Lyme bacterium called OspA that’s present in the tick’s gut. Since a tick must feed on someone for about 36 hours before the bacteria spreads to the victim, there’s time for antibodies created by the vaccine to attack the germs right at the source. Or so it seems from preliminary tests.

Another Lyme vaccine that operates differently is being developed by University of Massachusetts Medical School’s MassBiologics and should enter clinical testing soon.

More exciting is a vaccine under development at Yale that would recognize tick saliva and create a skin reaction that makes it harder for ticks to hang on and feed. That could prevent all tick-borne disease – not just Lyme – from being transmitted.

The U.S. previously had a human Lyme vaccine but it was pulled from the market in 2002 due to low sales caused by a combination of disappointing effectiveness and concern about side effects that some say were overblown. A Lyme vaccine has been available for dogs for many years.

No matter what vaccine is developed, the best defense against tick diseases is to try to keep them from grabbing on the first place by wearing long pants tucked into socks when walking through tall grass or among leaf litter, applying tick repellent on outdoor clothing when appropriate and checking yourself after being outdoors.

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