Varicella is generally perceived as a common and
benign disease. While this is true for most cases of primary VZV infection in
children, primary infection in adults (with a higher complication rate),
reactivation in elderly people (leading to herpes Zoster), congenital varicella
syndrome, disseminated neonatal varicella, and severe varicella in immunocompromised
patients are a major concern. European data based on hospitalization rate,
retrieval of sentinel system data, and centralized epidemiology reports, give
somewhat different figures in different Countries for the incidence and
complication rate following primary infection, indicating the need for a
combined prospective approach. Local conditions, social factors, age, and
seasonal shifts may all play a role in modifying varicella-related
complications. Yet, altogether, European data indicate that severe
complications of primary varicella infection are less frequent than reported in
the US, where approximately 7,000-10,000 hospitalizations and 100 deaths occur
each year for varicella. Importantly, annual hospitalization rate for Zoster
are up to 4-fold higher than for primary varicella, with a high rate of severe
and difficult-to-treat complications, such as post herpetic neuralgia. In
considering the public health benefit of a VZV vaccine, different
considerations must be taken into account. Prevention of Zoster, of varicella
infection in pregnancy, and of primary infection in adults and in
immunocompromised individuals are perhaps the most important public health
benefits. Data from high-risk, immunocompromised patients, indicate that the
VZV vaccine is effective in greatly (5-7 times) reducing the incidence and
severity of Zoster. However, there is a need for continuous surveillance on the
incidence of VZV-vaccine related Zoster, since the follow-up period for the
first vaccinated cohorts are not yet long enough to cover the median latency
time span of 30 years. Universal vaccination as a strategy to achieve all of
the goals indicated above should be weighed against the risks associated with
low vaccination coverage. In particular, coverage rates for recommended
vaccines such as mumps-measles-rubella (MMR) are still low in many European
Countries (Switzerland. 76%, Italy 50-60%, Germany 80%), with the consequence
that measles-related deaths are still higher than for varicella, and that a
shift has been observed towards primary infection in older groups of
susceptible individuals (something that should be avoided for varicella). While
it is important that higher coverage for MMR are reached in Europe before
universal varicella vaccination be considered, strategies targeted at specific
high-risk groups (including susceptible adults) warrant attention.
Economically, a universal vaccination program (with more than 90% coverage) has
been assessed by different studies on both sides of the Atlantic as cost-effective.
However, this is true mostly when taking into account indirect costs (usually
not at the expense of health care system), resulting from parental work loss,
that add up to 71-82% of the total average cost for each pediatric case of
primary varicella. Considering that 2-10% of vaccinees (the older the more) may
develop a vaccine-associated rash with or without fever and malaise, that a
proportion of vaccinees may develop breakthrough varicella, and that parents
might or might not lose work-days and seek medical attention for this
condition, a correct evaluation of the economical benefit of a universal
vaccination programme is difficult, and requires specific studies. A combined MMR-V vaccine would resolve
most of these problems related to universal vaccination, provided that
sufficient coverage is reached. Until then, vaccination strategies targeted to
specific groups would be beneficial and should be implemented.