Feb 28, 2024 ACIP Meeting - Polio Vaccines

The session begins with an introduction by Dr. Wharton, highlighting the reconvening of the polio vaccine session. Dr. Oliver Brooks, the chair of the Polio Vaccines Work Group, is acknowledged. The discussion focuses on the potential use of novel type 2 Oral Poliovirus (nOPV2) as an outbreak control measure in the United States, the fractional dose inactivated polio vaccine (fIPV), and determining the vaccine status of children who received it in other countries. Dr. Kidd, the CDC Work Group leader, presents on behalf of the group, acknowledging their work and chair Dr. Brooks. The background of poliovirus infection, its transmission, and the different types of polio vaccines (IPV and OPV) are discussed, emphasizing the need for substantial intestinal immunity to prevent gastrointestinal shedding, which IPV does not provide.

The paragraph discusses the global strategies for polio vaccination, particularly the shift to an IPV-only schedule in the United States since 2000. The continued circulation of wild poliovirus and vaccine-derived polioviruses in certain parts of the world is highlighted, along with the distribution of paralytic polio cases. The case of paralytic polio caused by a vaccine-derived poliovirus type 2 in Rockland County, New York, is discussed, emphasizing the link between this case and polioviruses collected in wastewater in Israel, the United Kingdom, and Canada. The importance of timely outbreak response with IPV is noted, along with the WHO recommendations for considering an OPV response if transmission persists.

The discussion focuses on the benefits and risks of using nOPV2, including its high seroconversion rates when administered to infants, particularly those who have already received IPV. The main benefit of nOPV2 is the conferral of gastrointestinal immunity, reducing fecal shedding following a subsequent oral challenge dose. The paper also addresses the risks associated with nOPV2, such as the low but non-zero risk of vaccine-associated paralytic polio (VAPP) and the potential for ongoing transmission of the nOPV2 virus, leading to a new vaccine-derived poliovirus type 2 (cVDPV2). The work group's considerations for the potential use of nOPV2 in the US, including the balance of risks and benefits, are discussed.

The paragraph presents modeling data from Kim Thompson and colleagues, which compares the expected number of paralytic cases under different mixing scenarios for a cVDPV2 outbreak. The results suggest that the use of any type of OPV2 would likely end transmission slightly earlier than with IPV alone, but the predicted reduction in paralytic cases is minimal. The work group's opinions on the reasonableness and feasibility of using nOPV2, including the need for FDA authorization and the challenges of tracking and containing every dose, are discussed. The potential impact of nOPV2 on health equity is also considered, with the work group acknowledging that the balance of undesirable consequences compared to desirable consequences might shift in the future depending on the size and scope of the outbreak.

The discussion revolves around the acceptability of nOPV2, considering public and stakeholder acceptance, especially in light of the previous removal of tOPV from the US vaccination schedule due to the unacceptable risk of VAPP. The work group's divided opinions on whether nOPV2 would be acceptable to key stakeholders and the impact on health equity are explored. The presentation concludes with the work group's consensus that the undesirable consequences of using nOPV2 during an outbreak in the US probably outweigh or are closely balanced with the desirable consequences, and that IPV is readily available in the US to protect against paralytic disease.

The paragraph includes a Q&A session where various concerns and questions about nOPV2 are raised. Dr. Kaslow from the FDA comments on the regulatory challenges of using nOPV2 in the US. Dr. Kotton raises concerns about the risk to immunocompromised individuals from community exposure to live viral vaccines. The discussion also touches on the potential impact of nOPV2 on undervaccinated communities and the overall acceptability of oral vaccines versus injectable ones. Dr. Chen emphasizes the need to address vaccine hesitancy in these communities and the precedent set in 2000 that any VAPP event is unacceptable.

The paragraph discusses the global switch from wild poliovirus type 2 and the introduction of fractional doses of IPV in routine immunization schedules in several countries due to limited IPV availability. The WHO's support for the use of two fractional doses of IPV as an IPV conservation strategy is highlighted. Clinical trial data suggests that two fractional doses are more immunogenic than one full dose of IPV but slightly less effective than two full doses, especially when administered at younger ages. The work group's recommendation on counting two fractional IPV doses as one full dose towards the US vaccination schedule is presented.

The final paragraph provides updates from various Health and Human Services (HHS) colleagues, including the Indian Health Service's efforts to prioritize vaccination and improve vaccine coverage rates, the passing of Dr. Jeff Kelman from CMS, updates on the COVID-19 and influenza vaccines from the FDA, and the ongoing work of the National Vaccine Injury Compensation Program (VICP) and the Countermeasures Injury Compensation Program (CICP). The NIH's update on vaccine-related research, including the value of maternal vaccine, ancillary benefits of COVID-19 vaccines, and studies on influenza and other diseases, concludes the meeting.