Vaccine News & Notes — August 2022

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How monkeypox spreads

While most cases of monkeypox identified during the current outbreak have been in men who have sex with men or those who are bisexual, a few cases have been diagnosed in children as well. This has led to some confusion, and misinformation, about how monkeypox is transmitted and who is at risk.

Monkeypox is primarily an infection found in animals. So, often when cases occur in people, it is because of exposure to the blood or body fluids from an infected animal, including from undercooked meat. However, monkeypox is also able to spread from person to person, as we are seeing in the current outbreak. This type of transmission can occur in several ways, including:

  • Exposure to an infected person’s respiratory secretions, especially following prolonged face-to-face or intimate contact (e.g., kissing, oral sex)
  • Direct contact with the rash
  • Contact with contaminated objects, such as clothing or bed linens
  • From an infected mom to her unborn baby through the placenta, during delivery, or by close contact after birth

While sexual partners can spread the virus to each other, the way this happens remains uncertain, meaning transmission could be via one of the above mechanisms due to intimate contact or it could be because bodily fluids exchanged during a sexual encounter contain the virus (or both). More studies are needed.

In sum, because of the variety of ways that monkeypox can spread, virtually anyone could be infected.

If you want to learn more about monkeypox, we recently wrote about the virus and the vaccines in our newsletter for healthcare providers, Vaccine Update.

Why the recent case of polio in the U.S. concerns virologists

In late July, the New York State Health Department reported that an unvaccinated individual who lives in Rockland County, New York, was paralyzed as a result of a polio virus infection. This was the first case of polio identified in the U.S. since 2013. The individual was infected with a type of polio that likely came from the oral polio vaccine (OPV).

OPV contains live, weakened polio virus, which offers benefits in terms of both individual and community immunity. But it also has one big drawback — on rare occasions (about 1 in 2.6 million doses), the vaccine virus reverts to its original form, regaining its ability to cause paralysis. Even when the vaccine virus does not revert, people who recently received OPV shed polio virus in their stools. As a result, the vaccine virus can spread to others. On one hand, this can be beneficial because some non-vaccinated individuals will also develop immunity after being exposed to the vaccine virus shed by recipients. This is particularly important in communities where it may be difficult to reach everyone with vaccination. On the other hand, it means that in rare cases, such as occurred in New York, someone who was not vaccinated can be exposed to the vaccine virus and it can revert to cause paralytic polio.

Children in the U.S. receive polio vaccine as a shot that contains dead polio virus, so the issues associated with OPV — viral shedding and reversion — cannot happen. However, because OPV is used in other countries, vaccine virus is still likely to enter the country through travel. Typically, we are not aware of this happening for two reasons. First, we do not routinely test wastewater for polio virus in the U.S., and second, because most of our population is vaccinated, we have high community immunity, making it difficult for polio virus to spread. Indeed, historically high polio vaccination rates in the U.S. are the main reason that the risk of having polio take hold in the U.S. is low. However, even a slight drop in immunization rates could quickly change that calculation.

Polio virus is very contagious. If we took 200 susceptible people on a trip and happened to encounter one person who was infected with polio, all 200 members of our group would likely be infected. Most of them (about 190) would not experience any symptoms. Of those who did feel ill, about 9 would experience mild symptoms for about a week, including sore throat, fever, nausea, vomiting, abdominal pain and constipation. Sadly, one individual would likely experience severe disease, resulting in muscle aches, spasms and paralysis. Rarely, the paralysis can result in death, particularly in older children and adults if they develop bulbar polio, a form of the disease in which paralysis is associated with the brain stem.

So, now you might be thinking, “If only about 1 of 200 susceptible people exposed to polio are likely to be paralyzed, and most of the U.S. population is vaccinated, why would virologists be concerned?” To them, this case of paralysis is like a canary in the coal mine. We know that immunization rates declined during the COVID-19 pandemic and some families have not yet gotten caught up, which means we have more susceptible people, specifically young children, than normal. We also know that polio and measles are among the most contagious vaccine-preventable diseases, so if we start to see cases of these infections, it is only a matter of time until we start to see a reappearance of other previously uncommon diseases thanks to vaccines.

With this in mind, if your family is caught up on vaccines, your family’s risk of polio, or other vaccine-preventable diseases, is low. However, if any family members are behind on the recommended vaccine schedule, especially young children, it would be a good time to make an appointment and start getting them caught up. Likewise, if your baby is too young to have received their early childhood vaccines, you will want to be even more vigilant about limiting their exposure to others, especially those who are ill or unvaccinated.

Hepatitis B vaccine is now recommended for most adults

Did you ever have a hepatitis B vaccine? Historically, only high-risk adults were routinely recommended to get this vaccine; however, as cases have continued, the Centers for Disease Control and Prevention (CDC) recently expanded the recommendation. Now, all adults up to 60 years of age who were not previously vaccinated against hepatitis B and those 60 years and older who want to be protected are recommended to get this vaccine. Since hepatitis B can cause chronic liver disease or liver cancer, the virus is more contagious than HIV, and the vaccine is safe and effective, adults can benefit from vaccination.

Find out more in the VEC’s new and updated hepatitis B materials:

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.