4.5 Chikungunya, Smallpox Vaccines

Chikungunya comes from the Makonde language in Africa and means

"that which bends up" or "bent over in pain"

Virus that causes Chikungunya

RNA virus of alphavirus Togaviridae

Chikungunya Symptoms

Abrupt onset, fever 39-40 Celsius, arthralgia of the small joints ( feet, hands, etc) in about 70% of cases, flush of face and trunk, followed by maculopapular rash, nausea, myalgia, vomiting, headaches, photophobia, conjunctivitis, retrobulbar pain, lymphadenopathy, average fatality rate is 0.4% (2.8% in children 1.6% in elderly)

Chikungunya is a ________ borne illness

mosquito

Chikungunya transmission

spread through the bite of Aedes mosquito (Aedes aegypti, Aedes albopictus) Same mosquito that transmits Dengue. Is a daytime urban mosquito.

Occurs in; Asia, Africa, Mexico, Caribbean, South America, Central America, Pacific Islands, and Southeastern US

Chikungunya Incubation

Typically, 3-7 days (range 1-12 days)

People at increased risk of Chikungunya

• Travel to countries with risk of chikungunya

• Higher risk itineraries

• Current outbreak situation

• >65 years old with underlying issues

• Long periods of exposure (6 months or more) cumulative

Ixchiq vaccine for Chikungunya: Type of Vaccine

Live attenuated vaccine for those 18 years of age and older

• CATMAT recommends against use in >65 years of age as of Dec 24 2025 due to serious adverse events they also suggest that if >65 should avoid travel to a Chikungunya outbreak region

Ixchiq vaccine Dose

1 dose IM

No boosters currently recommended

Ixchiq vaccine Efficacy

Seroconversion in >96% of individuals lasting at least 6 months (on going evaluations)

Ixchiq vaccine Contraindications

Immunocompromised

Age >65 (CATMAT)

Ixchiq vaccine Precautions

Pregnancy and breastfeeding vaccination should be deferred unless benefit significantly outweighs risks

Ixchiq vaccine AEs

Occur in >10% of patients, tenderness, headache, fatigue, arthralgia, fever and nausea some experience prolonged chikungunya type reactions

Note: CDC currently investigating reports of cardiac and neurologic events following vaccination in those >65

CANMAT age recommednation for Ixchiq vaccine

CATMAT only recommends for travelers 18 to 64 who are high risk of infection upon consultation with healthcare provider

• This is due to the higher risk of SAE

Virus that causes smallpox

variola virus of the Poxviridae family

Fatality rate of smallpox

Most devastating infection known killing up to 50% of infected population

Fatal in 8-10 days of symptoms

Last wildtyp case of smallpox

1958 the WHO launched a global eradication program

Last wildtype case was in Somalia in 1977

Declared eradicated in 1980

Where and how many samples of smallpox left

amples kept in only 2 laboratories (admit to owning) in Russia and the USA

Sequence is widely known and with today’s technology unfortunately extremely easy to replicate

How many doses left worldwide

Most developed countries keep stockpiles of vaccine against a biologic attack even 40+ years after eradication (50-90 million doses worldwide)

Imvamune Smallpox Vaccine Indications and Type and Dose

Live attenuated non-replicating vaccinia virus (closely related to variola)

Subcutaneous injection 0.5ml

Approved for use in related monkeypox infections in 2020

ACAM2000 Vaccine for smallpox: type, and how to administer

Authorized in December 2023

Live attenuated vaccine for >=16 years of age (note emergency use clarification)

Specialized training for injection by percutaneous scarification (uses a bifurcated needle with multiple punctures)

ACAM2000 vaccine AEs

erious side effects with use compared to most vaccines

Myocarditis and pericarditis in 5.7/1,000 doses

Neurologic, dermatologic, SJS, ocular scarring • Restricted access unless emergencies

Cause and Transmission of Monkeypox

Caused by the monkeypox virus of the Poxviridae family

Spread by body fluids, respiratory drops, virus contaminated objects (Fomites), infected animals

People at risk for Monkeypox

Risk of severe disease in young children, immunocompromised and pregnant females\\

Most cases in Canada a result of sexual contact with MSM being the highest risk at this time

Monkeypox severity

Usually self-limiting 14-28 days. Infectious until all lesions are scabbed over

Monkeypox vaccine and regimen and efficacy

Imvamune for 18 years and older

1 dose is thought to be 35-85% effective

2 dose is thought to be 65-85% effective

Vaccination is indicated for high-risk individuals

Individuals at high risk of mpox should receive two doses of Imvamune® administered at least 28 days (4 weeks) apart

People at risk of monkeypox

Men who have sex with men and meet the following criteria

• More than one partner

• Partner has more than one partner

• Has had confirmed STI in the past

• Has engaged in sexual contact in sex-on-premises venues\

Sex workers regardless of sexual orientation or sex assigned at birth

Staff of sex-on-premises

Those who engage in sex tourism

Monkeypox Post exposure prophylaxis recommendations

Post exposure immunization is recommended if they have not received 2 doses and had a high risk exposure to:

• Probable or confirmed mpox case

• Within a setting where mpox transmission is happening

Dose should be within 4 days of exposure but could be up to 14 days after

• Regardless of ongoing exposure status a second dose should be given 28 days later.