Introduction

The COVID-19 pandemic brought to the limelight the role international travel plays in the spread of diseases across national borders. A disease that originated in Wuhan, a city in China became global in a matter of months leaving in its trail a wave of destruction. Over time travel associated with politics, commerce, education, professional pursuit, tourism and health concerns continue to increase and this increases the risk of cross-border transfer of diseases. Before 2019, more than 1.4 billion people crossed international borders unlike 25 million in 1950. Travelling can place you at risk of vaccine-preventable diseases. It can also cause you to spread such diseases. 

Whether routine or destination-specific, vaccination has proven to be very helpful in preventing some travel risks due to vaccine-preventable diseases. Vaccination is the administration of an agent that provides immunity against a specific microorganism.¹ Vaccines come in different preparations- oral or injectable. While some vaccines are not age-specific, some others can only be given at some ages and in certain groups of people. There are country-specific requirements for travel vaccination and every traveler must get acquainted with it.

Types of travel health risks

International travel places the traveller at some risk.^2,3,4 These risks are:

• Health risks
• Environmental risks
• Safety and security risks

The health risks include the risk of:

• Airborne diseases
• Food and water-borne diseases 
• Vector-borne diseases
• Soil-borne disease
• Sexually transmitted diseases
• Blood-borne diseases
• Animal transmitted diseases(Zoonosis)

Some of these diseases can be prevented by vaccination, but there are some others, including some of the most important and most dangerous, for which no vaccines exist. ² 

The nature of the health risk depends on several factors. These include:

• Your underlying health and psychological state
• The presence of infectious diseases in the area
• Your local itinerary
• The nature of the accommodation
• The level of hygiene and sanitation in your destination city
• The behaviour of the traveller
• The duration of exposure 

Recommendations on travel vaccinations

Concerning travel vaccinationsm the World Health Organization(WHO) provides recommendations on these aspects:

• Routine vaccines before travelling
• Selective vaccines for specific travellers

Routine vaccine

Routine vaccines are the immunisations that are routinely provided as a part of normal health maintenance. These include vaccination against

• Poliomyelitis
• Diphtheria
• Measles
• Mumps
• Pertussis
• Rubella
• Rotavirus
• Tetanus
• Tuberculosis
• Hepatitis B
• Hemophilus influenza type b
• Seasonal influenza
• Pneumococcal disease
• Varicella
• Human papilloma virus.

These are incorporated in the National Immunization Programme schedule of most countries. The COVID-19 vaccine is considered routine In some countries like the United States.⁵

Selective or destination-specific vaccines

It is recommended to have these vaccinations to protect against prevalent diseases in the country of origin or destination. They are designed to protect travellers and prevent disease transmission within and between countries.

Vaccines for selective use include those against diseases like:

• Yellow fever
• Cholera
• Typhoid fever
• Rabies
• Japanese encephalitis
• Hepatitis A and E
• Tick-borne encephalitis
• Meningococcal disease

It is advised to have these vaccinations to guard against illnesses that are common in the country of origin or destination. They are meant to safeguard travellers and stop the spread of diseases both within and between countries.¹

Some nations require passengers to provide proof of vaccination at the entry or exit port and country immunisation requirements vary and may change over time.¹ Because country regulations are expected to vary over time, travellers must ensure that they know the requirements of the country to which they are travelling by contacting the relevant consulate or embassy.

To facilitate International travel, the WHO makes available the country list. This is a collection of essential facts to aid international travel. It provides information on country health requirements as well as WHO vaccination recommendations.⁶ 

Common travel-related diseases and required vaccinations

Typhoid fever

Transmission

The causative organism is the bacteria, Salmonella typhi. It is transmitted by drinking or eating contaminated water.

Vaccination protocol

Travelers to high-risk areas(Low-and-middle-income countries) are expected to receive the typhoid vaccine.⁷

The available vaccines are:

• Typhoid conjugate vaccine(TCV) vaccine – Given as a single injection, from six months of age upwards
• Vi-PS vaccine-It is an injectable vaccine. Given from two years of age upwards
• Ty21a vaccine – Given as oral capsules. Given from six years of age upwards

The vaccines should be given at least a month before travel.⁷

Neither of the Typhoid vaccines is 100% protective, so there is a need to take precautions when eating or drinking water in the destination country.

Yellow fever

Transmission

Yellow fever virus is transmitted through the bite of the Aedes or haemagogus specie of Mosquito.

Vaccination protocol

A single dose of live attenuated vaccine is required. It provides life immunity within a week in 95% of vaccinated people.

Yellow fever vaccination aims to

• Protect travellers to endemic areas(where the disease is prevalent) 
• Prevent international spread by minimizing the risk of importation of the virus to unaffected regions

The WHO recommends that all travellers greater than 9 months old in countries with evidence of periodic or persistent yellow fever virus transmission obtain the yellow fever vaccine. In most cases, passengers older than nine months who are arriving from nations where there is is a risk of yellow fever virus transmission—as well as occasionally those on transit through such countries —must provide proof of immunisation.

Poliomyelitis

Transmission

The causative organism is the wild poliovirus. It spreads from person to person via the faecal-oral pathway.

Vaccination protocol

There are three types of polio vaccine currently in use:

• Inactivated polio vaccine
• Bivalent oral polio vaccine
• Monovalent oral polio vaccine

The oral polio vaccine is given in three or four doses. The full dose gives 100% protection.

Travellers from polio-free to polio-endemic nations must complete the polio vaccine according to their national immunisation schedule.

Furthermore, travellers from such countries should obtain a dose of oral poliovirus vaccine (OPV) or inactivated poliovirus vaccine (IPV) at least four weeks before (and within a year of) departure. ⁶ Some polio-free countries require resident travellers and long-term visitors from polio-affected countries to:

• Submit documentation of recent vaccination against polio
• Receive an additional dose of polio vaccine upon arrival
• Or have both

Cholera

Transmission

The causative agent for Cholera is the bacteria, Vibrio cholerae. It is transmitted through the faeco-oral route through contaminated food or drinks.

Vaccination protocol

There a three(3) WHO-approved oral vaccines- 

• Dukoral®, 
• Shanchol™, 
• and Euvichol®

Dukoral® is primarily used for travellers and can be administered to individuals over the age of two years.

This vaccine requires;

• Two doses for full protection
• Administration at intervals of seven(7) days to six(6) weeks

The Dukoral® vaccine protects for two years.

Pre-travel preparations

The travel preparations should start at least six weeks before travel. 

This is because;

• Some vaccines require days or weeks to become effective
• You may need some weeks to get the full dose
• You may not have the vaccine in your locality and may need to travel distances to access a designated vaccination venue

Before travelling, you should obtain the following information on the destination country

• Vaccine requirements
• Disease outbreaks
• Political environment
• Available medical resources

A scheduled visit to your health care provider or travel health specialist is needed.⁴

The aim of the review is for you to;

• Receive further information on destination-specific vaccination
• Discuss your health concerns
• Discuss your travel schedule at the destination.
• Receive specific advice and recommendation

At the end of the consultation, you should make sure that you are:

• Up-to-date with the routine vaccination
• You’ve taken the travel-specific vaccines at the designated centres
• On the lookout for breaking news on disease outbreaks in your destination country

Post-travel health considerations

When you return from your trip, you should;

• Monitor your health closely
• Report any unexpected symptoms to your healthcare physician.
• Take follow-up vaccinations and boosters
• Continue long-term health monitoring

Special considerations for specific groups

Children and infants

Vaccinating children for travel requires careful evaluation. Whenever possible, children should receive standard childhood immunisations on a regular basis. Travel at an earlier age, however, might require giving some of the vaccines before schedule.⁸

Pregnant women

Pregnant women are prone to vaccine-preventable diseases just as every other person. They may even be more at risk because of the reduced immunity in pregnancy.

There are three categories of vaccines for pregnant travellers

• Routinely recommended vaccination
• Selected vaccination based on travel itinerary
• Vaccines required by International health regulations or for entry into the destination country

Vaccination is needed for some infections like tetanus, diphtheria and pertussis in pregnancy. This protects both the mother and the unborn baby.

Except for live vaccinations, there have been no safety concerns regarding travel-related vaccines during pregnancy.^9,10

Live vaccines are the yellow fever vaccines, MMR(measles, mumps, rubella), oral polio, oral typhoid and BCG. They are dangerous because there is a theoretical risk that the virus may cross the placenta to infect the unborn baby.

Pregnant women should avoid travel to areas at high risk of the disease. If travel is unavoidable, you should contact your health provider. In such circumstances, your doctor may prescribe the vaccine if the benefits exceed the risks. 

Elderly and Immunocompromised(weakened immune system) Travelers

Most vaccines are safe for these groups of travellers, however, live vaccines are not safe for the immunocompromised(those with reduced immunity).¹¹

Examples of immunocompromised people are people with:

• Human Immunodeficiency Virus(HIV)
• Certain types of cancers
• Those on chemotherapy
• Those with some form of autoimmune disease
• Congenital immunodeficiency

Vaccines against the bacteria, Streptococcus pneumoniae and influenza are strongly recommended for most immunocompromised patients as they are at a higher risk of infection from these organisms.

If you are elderly or immunocompromised:

• Verify the health information of your destination country
• Make an appointment with your healthcare provider
• Discuss any chronic medical condition with your doctor¹²
• Discuss your itinerary
• Take all recommended vaccines

Your health provider may ask for a waiver if the risk of taking certain vaccines is greater than the benefit.

FAQ’s

Can you get travel vaccines while pregnant?

Pregnancy does not prevent you from receiving vaccines when travelling. Your health provider will help you in choosing the safe vaccine for you.

How long am I protected after vaccination?

The duration of protection after vaccination depends on the type of vaccine.

What happens if I am not vaccinated?

If you are not vaccinated, you are at risk of spreading the disease to unaffected areas. You can also get sick or even die from vaccine-preventable diseases. 

Summary

Travel-associated spread of infectious diseases is a threat to global health. Vaccination provides the cornerstone for combating a variety of infectious diseases. Fortunately, adherence to vaccination protocols has been instrumental in stemming the tide. A responsibility is laid on the traveller to seek the correct information, get a medical review before travel and adhere to all travel vaccine-related instructions.