Poliomyelitis Virus Type 2

Usage

Poliomyelitis Virus Type 2, specifically the novel Oral Polio Vaccine type 2 (nOPV2), is used for active immunization against poliomyelitis caused by type 2 poliovirus. It is primarily deployed during outbreaks as part of emergency response efforts, especially when dictated by the Global Polio Eradication Initiative (GPEI) or WHO. The inactivated polio vaccine (IPV) containing all three serotypes (1,2 and 3) is used for routine immunization.

• Pharmacological classification: Viral vaccine, live attenuated.

• Mechanism of action: nOPV2 contains a weakened form of the type 2 poliovirus. Oral administration allows the virus to replicate in the gut, stimulating an immune response without causing paralytic disease. This generates protective antibodies against future exposure to wild-type poliovirus type 2.

Alternate Names

• nOPV2 (novel Oral Polio Vaccine type 2)
• Monovalent Oral Poliovirus Vaccine Type 2 (mOPV2)

How It Works

• Pharmacodynamics: nOPV2 stimulates both humoral and cellular immunity against type 2 poliovirus. It induces the production of neutralizing antibodies, primarily IgG and IgA, which prevent viral attachment and entry into cells. It also activates T-cells, contributing to long-term immunological memory.

• Pharmacokinetics: Administered orally, the vaccine virus replicates in the gastrointestinal tract. It is shed in feces, which can contribute to indirect immunization of others in close contact (passive immunization). Systemic absorption is minimal, and the attenuated virus does not typically spread to the central nervous system. Elimination is primarily through fecal shedding and immune clearance.

Dosage

Standard Dosage

nOPV2 is administered orally as two drops (0.1 mL) per dose. The standard regimen for outbreak response involves two doses given four weeks apart. Clinical trials have also investigated single and three-dose regimens.

Adults:

Two drops (0.1 mL), orally. Two doses are given four weeks apart during outbreak response.

Children:

Two drops (0.1 mL), orally, following the same schedule as adults.

Special Cases:

• Immunocompromised Individuals: Contraindicated for individuals with severe immunodeficiency. IPV is the preferred vaccine in these cases.

• Pregnant Women: Not recommended during pregnancy due to theoretical risks, unless there’s a high risk of exposure.

• Breastfeeding Mothers: No data available on secretion in breast milk.

Clinical Use Cases

The primary use of nOPV2 is during outbreaks of type 2 poliovirus. It is not typically used in the clinical settings mentioned (Intubation, Surgical Procedures, Mechanical Ventilation, ICU Use, Emergency Situations)

Dosage Adjustments:

No specific dosage adjustments beyond considerations for immunocompromised individuals, pregnant women, and breastfeeding mothers, as outlined above.

Side Effects

Common Side Effects:

nOPV2 is generally well-tolerated.

Rare but Serious Side Effects:

Vaccine-Associated Paralytic Poliomyelitis (VAPP) is a rare but serious adverse event associated with OPV, including nOPV2.

Long-Term Effects:

No long-term adverse effects specifically associated with nOPV2 have been identified.

Adverse Drug Reactions (ADR):

VAPP is a rare ADR requiring prompt medical attention.

Contraindications

• Hypersensitivity to any component of the vaccine.
• Severe immunodeficiency (primary or acquired, including patients receiving immunosuppressive therapy).

Drug Interactions

• Immunosuppressants: Concurrent use can reduce the immune response to nOPV2 and increase the risk of VAPP. Immunization should be deferred until after immunosuppressive therapy is completed.
• Other Live Vaccines: Administering nOPV2 within one month of other live vaccines can interfere with the immune response. If possible, separate live vaccines by at least four weeks.

Pregnancy and Breastfeeding

nOPV2 is not recommended for pregnant women unless the benefit outweighs the risk in a high exposure situation. Data regarding use during breastfeeding is limited.

Drug Profile Summary

• Mechanism of Action: Live attenuated vaccine stimulating immunity against type 2 poliovirus.
• Side Effects: Generally well-tolerated. Rarely, VAPP.
• Contraindications: Hypersensitivity, severe immunodeficiency.
• Drug Interactions: Immunosuppressants, other live vaccines.
• Pregnancy & Breastfeeding: Not generally recommended during pregnancy. Limited data for breastfeeding.
• Dosage: Two drops orally, two doses four weeks apart during outbreak response.
• Monitoring Parameters: Monitor for adverse events, particularly VAPP.

Popular Combinations

nOPV2 may be used in conjunction with other polio vaccines (bOPV or IPV) in certain outbreak control strategies.

Precautions

• Screen for contraindications before administration.
• Adhere to strict hygiene practices during administration to avoid contamination of the multi-dose vial.
• Closely monitor recipients for any adverse events.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Poliomyelitis Virus Type 2 (nOPV2)?

A: Two drops (0.1 mL) orally, typically administered as two doses four weeks apart in outbreak situations.

Q2: What are the contraindications for nOPV2?

A: Contraindications include hypersensitivity to any vaccine component and severe immunodeficiency.

Q3: Can nOPV2 be given during pregnancy?

A: nOPV2 is generally not recommended during pregnancy unless the risk of polio exposure outweighs the potential risks to the fetus.

Q4: What is VAPP and how is it related to nOPV2?

A: VAPP (Vaccine-Associated Paralytic Poliomyelitis) is a rare but serious adverse event that can occur after administration of oral polio vaccines, including nOPV2. It involves the development of paralysis similar to that caused by wild poliovirus.

Q5: How is nOPV2 different from IPV?

A: nOPV2 is a live attenuated vaccine administered orally, while IPV (Inactivated Polio Vaccine) contains inactivated poliovirus and is given by injection. IPV is used for routine immunization and is safer for immunocompromised individuals.

Q6: What are the drug interactions to be aware of with nOPV2?

A: nOPV2 can interact with immunosuppressants, which may reduce the immune response and increase the risk of VAPP. It should also be administered at least four weeks apart from other live vaccines.

Q7: What is the role of nOPV2 in polio eradication?

A: nOPV2 is a critical tool for controlling outbreaks of type 2 poliovirus, aiding in global eradication efforts. Its targeted use helps prevent the resurgence of this specific serotype.

Q8: Can nOPV2 be administered with other polio vaccines?

A: Yes, nOPV2 can be used in conjunction with other polio vaccines like bOPV or IPV as part of specific outbreak control strategies, as recommended by public health authorities.

Q9: What is the duration of protection after receiving nOPV2?

A: The duration of protection conferred by nOPV2 is not yet fully established. However, it is expected to provide significant protection against type 2 poliovirus, especially after completing the recommended dosage schedule.