[5] In cases of biological contagions such as influenza, measles, and chicken pox, immunizing a critical community size can provide protection against the disease for members who cannot be vaccinated themselves (infants, pregnant women, and immunocompromised individuals).
[9][10] More recently researchers have looked at exploiting network connectivity properties to better understand and design immunization strategies to prevent major epidemic outbreaks.
[1][14] In circumstances where vaccines are scarce, efficient immunization strategies become necessary to preventing infectious outbreaks.
These nodes are the most highly connected in the network, making them more likely to spread the contagion if infected.
[citation needed] Millions of children worldwide do not receive all of the routine vaccinations as per their national schedule.
A Cochrane review assessed the effectiveness of intervention strategies to boost and sustain high childhood immunization coverage in low- and middle-income countries.