Live attenuated oral polio vaccine (OPV) and inactivated polio vaccine (IPV) are the tools being used to achieve eradication of wild polio virus. Because OPV can rarely cause paralysis and generate revertant polio strains, IPV will have to replace OPV after eradication of wild polio virus is certified to sustain eradication of all polioviruses. However, uncertainties remain related to IPV's ability to induce intestinal immunity in populations where fecal-oral transmission is predominant. Although substantial effectiveness and safety data exist on the use and delivery of OPV and IPV, several new research initiatives are currently underway to fill specific knowledge gaps to inform future vaccination policies that would assure polio is eradicated and eradication is maintained.

A public health catch-22: In 2016, the serotype 2 component of the oral poliovirus vaccine given to children was withdrawn. This measure was taken to prevent vaccine-associated disease outbreaks caused by mutation in the live attenuated vaccine. Children around the world now have poor immunity to serotype 2 poliovirus because the inactivated vaccine is far less effective and a new oral vaccine is not yet ready. Using a statistical model, Macklin et al. discovered that most current outbreaks of polio in several countries across Asia and sub-Saharan Africa are likely associated with the serotype 2 vaccine strain (see the Perspective by Donlan and Petri). To block transmission when poliovirus outbreaks occur requires deployment of the only tool in the box: the existing live attenuated serotype 2 oral vaccine, which increases the risk of vaccine-derived disease. Science , this issue p. 401 ; see also p. 362

We challenge the notion that influenza B is milder than influenza A by finding similar clinical characteristics between hospitalized adult influenza-cases. Among patients treated with oseltamivir, length of stay and mortality did not differ by type of virus infection.

Background: Little information is available describing the epidemiology and clinical characteristics of those <12 months hospitalized with influenza, particularly at a population level. Methods: We used population-based, laboratory-confirmed influenza hospitalization surveillance data from 2003 to 2012 seasons to describe the impact of influenza by age category (<3, 3 to <6 and 6 to <12 months). Logistic regression was used to explore risk factors for intensive care unit (ICU) admission. Adjusted age-specific, influenza-associated hospitalization rates were calculated and applied to the number of US infants to estimate national numbers of hospitalizations. Results: Influenza was associated with an annual average of 6514 infant hospitalizations (range 1842–12,502). Hospitalization rates among infants <3 months were substantially higher than the rate in older infants. Most hospitalizations occurred in otherwise healthy infants (75%) among whom up to 10% were admitted to the ICU and up to 4% had respiratory failure. These proportions were 2–3 times higher in infants with high risk conditions. Infants <6 months were 40% more likely to be admitted to the ICU than older infants. Lung disease (adjusted odds ratio 1.80; 95% confidence interval 1.22–2.67), cardiovascular disease (adjusted odds ratio: 4.16; 95% confidence interval: 2.65–6.53), and neuromuscular disorder (adjusted odds ratio: 2.99; 95% confidence interval: 1.87–4.78) were risk factors for ICU admission among all infants. Conclusions: The impact of influenza on infants, particularly those very young or with high risk conditions, underscores the importance of influenza vaccination, especially among pregnant women and those in contact with young infants not eligible for vaccination.