Why isn’t there a norovirus vaccine?
The development of a norovirus vaccine is a very challenging task.
One of the main reasons there is no norovirus vaccine yet is the nature of the virus itself. Norovirus mutates fast, and there are many subtypes of norovirus. An effective vaccine would have to target all strains. Production of such vaccines is problematic [1, 2, 3, 4].
Another obstacle in the development of a norovirus vaccine is the immune response. The immune reaction to the infection is short-term and strain-specific [1, 2].
Also, some technical problems are a hurdle in norovirus vaccine development. For example, cell and animal models for human infecting noroviruses are missing. These make it hard to test the candidate vaccines [2, 3].
Norovirus vaccines in development
The production of a norovirus vaccine is a daunting process. However, despite all the challenges, potential vaccines are in development. Some of them are already in clinical trials [5, 6, 7].
The potential norovirus vaccines use recombinant adenoviruses, P particles, and virus-like particles [6, 7].
However, it is still unclear whether the potential vaccines will work against all or most of the norovirus strains [8].
Also, it is unclear if the vaccines will give suitable protection to all age groups and how long they will work [8].
Is norovirus threat?
Yes, norovirus is a threat. It leads to endemics and the epidemic of gastroenteritis.
Norovirus is responsible for more than half of the yearly viral outbreaks (excluding the COVID-19 pandemic) [9].
Particularly dangerous spread of norovirus occurs in schools, kindergartens, and hospitals. These half-closed communities allow the virus to spread fast [9]. Other high-risk places are hotels and cruise ships.
The norovirus infection is dangerous, especially in infants, the elderly, and immunocompromised people. In this population, the viral infection can be prolonged and severe [9, 10, 11].
Around 1 in 10 norovirus-infected people have a severe course of the disease [12].
Symptoms of a norovirus infection
Symptoms of a norovirus infection start typically between 12 and 48 hours after infection [13].
The most common symptom of norovirus infection is diarrhea. It can be severe and lead to dehydration [14].
Other symptoms of norovirus infection include:
In infants, a norovirus infection can lead to sleepiness, irritability, and low urine production [13]. The last is a sign of dehydration.
A general complication of norovirus infection is dehydration [13]. Dehydration can be life-threatening for infants, older people, and immunocompromised people.
Severe cases of norovirus in people with compromised immunity can lead to chronic diarrhea. It can last for a long time, ranging from several weeks to several years. Chronic diarrhea can cause impair the body's ability to absorb food, resulting in weight loss. In young children, it can lead to growth problems [15].
A norovirus infection can also cause neurological problems. The virus can lead to episodes of seizures and encephalopathy [16].
In preterm infants, norovirus infection can lead to necrotizing enterocolitis. It is a serious and dangerous condition that results in intestinal damage [17, 15].
How can I get norovirus?
Norovirus is highly contagious. Only 18 viral particles are enough to cause the disease [13].
Among the ways of transmission are:
- contact with the infected person,
- fecal-oral way,
- vomits-oral way,
- sharing food and drinks with the infected person,
- sharing food utensils with the infected individual [13].
Another common way of norovirus spreading is through contaminated food and water. It can happen when the food or water is prepared in low-sanitary conditions [14].
Also, it is possible to get a norovirus after touching a surface with the virus and then the mouth [14].