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ARTICLE

Risk for Cancer-Causing Infections Highest in Low- and Middle-Income Countries

AUG 10, 2017 | DEANNA KEPKA, PHD, MPH

Human Papillomavirus, HIV Co-Infection, and Human Herpesvirus

Among women around the world, more than half of all cancers attributed to infection are caused by HPV.1 High rates of coinfections and limited access to health care resources influence the disproportionate incidence of many preventable cancers in low-income countries, HPV included.

In these countries and for both sexes combined, HPV is responsible for half of infection-attributable cancers. Further, the higher incidence and mortality due to cervical cancer in low-income countries results from high rates of co-infection with HIV and poor access to timely cervical cancer screening, as well as recommended treatment procedures for precancerous lesions.1 In addition, although HHV-8 only accounts for 2% of infection-driven cancers worldwide, in low-income countries, that rate jumps to 14%. Similar to cervical cancer, high rates of HIV infection without access to combined antiretroviral therapy exacerbates the risk for Kaposi’s sarcoma due to HIV co-infection with HHV-8.1,4
 

Hepatitis B

Hepatitis B, on the other hand, infects more than 2 billion people around the world, with more than 300 million of these individuals living as chronic HBV carriers. HBV infection is highest in sub-Saharan Africa, China, Korea, and Taiwan, as well as many countries in South­east Asia and the Amazon basin. Where HBV infection is endemic, the lifetime risk of HBV infection is 60%, with most infections occurring from child-to-child (horizontal) and perinatal (vertical) transmissions.3
 

Cancer Prevention Vaccines

Unfortunately, we do not have all-encompassing solutions for the prevention of most of the can­cers caused by oncogenic infections worldwide. However, we do have 2 vaccines that, if adminis­tered globally, could prevent 50% of the cancers caused by oncogenic infections, totaling more than 1 million cancer cases (Table1, 3, 10, 11). In the United States, the HPV vaccine has been avail­able for more than a decade and the HBV vaccine has been available for more than 3 decades. Im­proving receipt of these vaccines in the regions of the world that would benefit most from their availability is a difficult but critical challenge.
 

Hepatitis B Vaccines

The World Health Organization (WHO) recently published The Global Hepatitis Report, 2017,5 which underscores 3 key strategies designed to eliminate hepatitis infection as a public health threat by 2030 and aims to implement well-designed global health approaches to treat, test, and prevent chronic hepatitis infection. According to WHO, the eliminations of hepatitis as a public health threat will be reached when we have a 65% reduction in mortality due to hepatitis and a 90% reduction in incidence of hepatitis infection from baseline 2015 global estimates.5 Five virus types cause most cases of viral hepatitis; however, only HBV, HCV, and hepatitis D virus cause chronic hepatitis, which may result in cirrhosis of the liver and lead to primary liver cancer (hepatocellular carcinoma).

HBV and HCV cause 96% of all deaths due to viral hepatitis.5 HBV is preventable with timely receipt of safe and effective vaccines.5 WHO recommends that all infants receive their first dose of the HBV vaccine within 24 hours of being born, as timely receipt of this dose can prevent mother-to-child transmission. The birth dose should be followed by another 2 or 3 doses to complete the recommended immu­nization series.6 Worldwide, in 2015, 3-dose coverage of the HBV vaccine has reached 84% while the birth dose vaccination rate continues to be low, at 39%.5 Since the introduction of the vaccine, chronic HBV among children under age 5 dropped from 4.7% in the prevaccination era (1980s to early 2000s) to 1.3% in 2015. In most of Africa, even following the vaccination era, chronic HBV infection rates remained at 3% in 2015, ranking among the highest worldwide.5


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