Immunization Module: Antiviral Vaccines

Study Session 3  Antiviral Vaccines

Introduction

In this study session, you will learn about the antiviral vaccines that are in common use for preventing viral diseases in most developing countries, including Ethiopia, and the recommended dosages and schedules for immunization with these vaccines. There are many other antiviral vaccines available in the world that are not widely used in developing countries, so we will concentrate here on the common antiviral vaccines available for the Expanded Programme on Immunization (EPI) in Ethiopia. These are hepatitis B (HepB) vaccine, oral polio vaccine (OPV) and measles vaccine. You will also be reminded about the need to give vitamin A supplements at the same time as the measles vaccine, and to children who present to you with measles. Then we describe one of the newer antiviral vaccines against rotavirus, which is being added to the EPI. Finally, we mention yellow fever vaccine, which is not in the EPI but may be required for travel abroad.

Studying this session will enable you to give clear information to the people in your community about the value of immunizing their children with these vaccines, which prevent long-term disability and save many millions of lives. You will be able to tell parents that these vaccines are very safe, and any adverse events following immunization are almost always very mild and easily treated. We will also describe the contraindications that mean you should not immunize a child, either temporarily or permanently.

To guarantee long-term protection, all doses of the antiviral EPI vaccines should be given. If a child misses the scheduled date for an immunization, he or she should be given the missed dose as soon as possible. There is no need to re-start the immunization schedule.

Learning Outcomes for Study Session 3

When you have studied this session, you should be able to:

• 3.1  Define and use correctly all of the key words printed in bold. (SAQ 3.1)
• 3.2  Describe the common antiviral vaccines available in the Expanded Programme on Immunization (EPI) in Ethiopia, and the new rotavirus vaccine that will become available soon. (SAQ 3.2)
• 3.3  Describe the storage, dosages and schedules of the common antiviral EPI vaccines, and the dosage of vitamin A given routinely with measles vaccine or to children with measles. (SAQs 3.2, 3.3 and 3.4)
• 3.4  Describe the possible adverse events following immunization with the antiviral EPI vaccines and how you manage them at Health Post level. (SAQ 3.3)
• 3.5  Describe the contraindications for the antiviral EPI vaccines. (SAQ 3.5)

3.1  Hepatitis B vaccine (HepB)

3.1.1  What is HepB vaccine?

Hepatitis B diseases are discussed in Study Session 4 of the Communicable Diseases Module, Part 1.

Hepatitis B (HepB) vaccine protects against the hepatitis B diseases, which affect the liver and are caused by hepatitis B viruses. If a child is infected with hepatitis B viruses, liver disease may develop many years later in adult life. In Ethiopia, HepB vaccine is routinely given to infants as one of the five vaccines combined in the pentavalent vaccine (which also protects against diphtheria, pertussis, tetanus and Haemophilus influenzae type b). The four antibacterial vaccines in the pentavalent vaccine used in Ethiopia were described in Study Session 2.

HepB vaccine is also available on its own as a single vaccine, which may be given to healthworkers as a ‘booster’ to increase their protection against infection by bloodborne hepatitis B viruses from patients. The vaccination schedule in adults is not the same as the schedule you already know for infants, who receive HepB vaccine as part of the pentavalent vaccine in the Ethiopian EPI.

The HepB component of the pentavalent vaccine is very safe and effective: up to 95% of infants who receive all three doses of pentavalent vaccine are protected against hepatitis B virus infection. The contraindications are the same as already described for pentavalent vaccine: infants with a high-grade fever should not be vaccinated until they recover. An infant who develops a severe allergic reaction, swollen lymph glands or encephalopathy to a previous dose of pentavalent vaccine should not be given another dose.

3.2  Oral polio vaccine (OPV)

3.2.1  What is OPV?

You will learn more about the oral administration of vaccines in Study Session 4.

Oral polio vaccine (OPV) is made from live-attenuated polioviruses (note that ‘poliovirus’ is all one word). OPV is a light red or light yellow liquid supplied in vials that either have droppers as caps, or they come with separate glass droppers. The vaccine is given by putting two drops into the child’s mouth (Figure 3.1).

Figure 3.1  A child receiving oral polio vaccine drops. (Photo: UNICEF Ethiopia/Indrias Getachew)

Poliomyelitis is described in Study Session 4 of the Communicable Diseases Module, Part 1. It has been eliminated by vaccination in many countries and the WHO aims to eradicate it from the world.

OPV gives protection against the three types of polioviruses (types 1, 2 and 3) that cause poliomyelitis (polio) — a crippling disease of the brain and spinal cord.

Note that the vaccine used for routine immunizations in the EPI is not the only type of OPV available. Other types may be issued to control outbreaks of polio if they occur, but are not used for routine protection of infants; these vaccines should be returned to the central store after the supplementary immunization campaign.

3.2.2  Storage, dosage, schedule and effectiveness of OPV

Store OPV between +2°C and +8°C; but it may be frozen for long-term storage.

Four doses are given, each of two drops. OPV should be given at birth, 6 weeks, 10 weeks and 14 weeks of age. The interval between all doses must be at least four weeks. The birth dose is known as OPV0; the subsequent doses are referred to as OPV1 (at 6 weeks), OPV2 (at 10 weeks), and OPV3 (at 14 weeks).

You should not give OPV0 (the birth dose) to an infant who is more than 14 days old. If this dose has not been given by 14 days, miss this dose and wait until the child is six weeks old, and then give OPV1. You should also give the first doses of the other routine EPI vaccines, including PCV10, at six weeks. The remaining doses should be given as scheduled at 10 and 14 weeks.

If a child spits out the vaccine drops, or vomits immediately after a dose of OPV, it is quite safe to repeat the dose. You should still give the scheduled dose even if a child has diarrhoea at the time; give OPV as usual, but administer an extra (fifth) dose at least four weeks after he or she has received the final dose in the schedule. Ninety-nine per cent of those who are vaccinated with four doses of OPV are protected from polio for life, but during campaigns children are often given additional boosters of OPV to ensure high herd immunity.

3.2.3  Contraindications of OPV and adverse events

OPV is a very safe vaccine and there is no contraindication to prevent giving it. Serious adverse reactions to OPV are very rare: acute flaccid paralysis has been reported in approximately one child in every 1–10 million children who have been vaccinated with OPV. Table 3.1 summarises what you should know about OPV.

3.3  Measles vaccine

3.3.1  What is measles vaccine?

Measles is discussed in Study Session 4 of the Communicable Diseases Module, Part 1.

Measles vaccine is made from live-attenuated virus and is supplied as a powder that has to be reconstituted with (dissolved in) the special diluent provided to use with it. You will learn about vaccine reconstitution in detail in Study Session 4.

Measles is a highly infectious disease caused by a virus that weakens the immune system, leaving children susceptible to other dangerous childhood infections. The common signs and symptoms of measles are a red skin rash, runny nose and conjunctivitis (Figure 3.2).

Figure 3.2  (a) Measles rash covering the whole body of a child; (b) Conjunctivitis (red, watery eyes) caused by measles. (Photos: WHO and Ethiopian Federal Ministry of Health, 2005, Case Definition of Measles)

3.3.2  Storage, dosage and schedule of measles vaccine

The vials containing the dry measles vaccine powder can be frozen for long-term storage, but after reconstitution with the correct diluent, measles vaccine should be kept at between +2°C and +8°C, and never frozen. Any remaining reconstituted vaccine must be thrown away after six hours, or at the end of the immunization session, whichever comes first.

One dose of 0.5 ml of measles vaccine is injected subcutaneously (into the fatty layer below the skin and above the muscle) in the outer upper arm as soon as possible after nine months of age. Waiting this long is advisable because the maternal antibodies against measles that are transferred to the unborn baby before birth last longer in the blood of the baby than other antibodies. As a result, immunization with measles vaccine is often not effective before nine months of age. The aim in the EPI in Ethiopia is to give measles vaccine to all children at nine months of age. To achieve high-level population immunity, a second dose is ideally given after 12 months of age during supplementary immunization activities.

In special situations, for instance in measles outbreaks, in emergencies such as in refugee camps with high measles transmission, or among HIV-infected children, an ‘early’ extra dose of measles vaccine may be given at six months. If a child has received measles vaccine before nine months of age, a second dose should be administered at nine months, or as soon as possible afterwards. All children should ideally receive a supplementary dose of measles vaccine after 12 months of age as part of measles elimination campaigns.

3.3.3  Effectiveness of measles vaccine

Measles vaccine is highly effective at preventing measles; 85% of infants who are immunized at 9 months are protected from measles for the rest of their lives; vaccine efficacy rises to 95% after a second dose after 12 months of age. In the year 2000 there were an estimated 750,000 deaths from measles worldwide. By 2008, vaccination campaigns had succeeded in reducing this number by 75%. The World Health Organization (WHO) estimated that in 2008 around 83% of the world’s children were receiving one dose of measles vaccine by their first birthday.

3.3.4  Contraindications for measles vaccine, adverse events and how to manage them

Children who develop a severe allergic reaction should be referred immediately to a health centre, and should not be given measles vaccine again.

In around 20% of children, a mild fever lasting one to three days may occur approximately one week after immunization. A few children (less than 5%) develop a mild rash. Injection-site abscess or severe allergic reactions including rash, breathing difficulty and fainting occur very rarely. Table 3.2 gives a summary of the possible adverse events following measles vaccination and how to manage them.

Table 3.3 summarises what you should know about measles vaccine.

3.3.5  Vitamin A supplements and measles prevention

It is important to know that in countries such as Ethiopia where vitamin A deficiency frequently occurs among children, vitamin A should be given routinely every six months. If a child has not previously received a vitamin A supplement, it should be given at the same time as the measles vaccine. This is because measles increases the risk of blindness due to vitamin A deficiency. Signs of vitamin A deficiency are white spots on the sclera (white part of the eye) and clouding of the cornea (the thin tissue covering the black centre of the eye and the coloured parts around it). In severe cases, blindness results.

Do not put the vitamin A capsule into the child’s mouth, or allow the child to swallow the capsule.

Vitamin A is supplied in capsules of 100,000 IU (international units, which is the standard measurement for vitamin doses). Each capsule has a nipple at one end. The drops are given by cutting across the middle of the nipple with scissors and immediately squeezing the drops into the child’s mouth (Figure 3.3 on the next page). Vitamin A drops are also given in Child Health Days to ensure the dose is repeated every six months, until the child reaches five years.

Figure 3.3  A child receiving vitamin A drops at a scheduled immunization clinic where he will also receive measles vaccine. (Photo: UNICEF Ethiopia/Indrias Getachew)

The routine dose of vitamin A for a child aged 6–11 months is the drops from one capsule (100,000 IU); the drops from two capsules (200,000 IU) are given to children aged 12–59 months at regular intervals, every six months. This ensures that all children are fully protected from the harmful effects of vitamin A deficiency.

3.4  Rotavirus vaccine

Rotavirus vaccine is one of the new antiviral vaccines that should soon become available as part of the routine EPI in Ethiopia. Rotaviruses are the leading cause of severe diarrhoeal disease and dehydration among children in many developed and developing countries. The WHO estimates that 20% of child deaths under five years from diarrhoeal diseases worldwide are due to rotavirus infection — most of them in countries like Ethiopia. Globally, more than 125 million cases and up to 610,000 deaths annually are due to rotavirus diarrhoea.

3.4.1  Dosage and schedule of rotavirus vaccine (Rotarix^TM)

Two new live-attenuated rotavirus vaccines have been licensed for use in routine immunization programmes. They are both given orally to infants as drops into the mouth. The vaccine chosen for the EPI in Ethiopia is known by its brand name Rotarix^TM. It is a liquid suspension vaccine, supplied in single-dose ‘squeeze-tube’ vials.

Rotarix^TM is given in two oral doses, each of 1.5 ml, at the following time intervals:

• First dose at 6 weeks of age, but no later than 12 weeks
• Second dose at least 4 weeks after the first dose
• The two-dose schedule should be completed by 16 weeks, but no later than by 24 weeks of age.

Note that the ideal schedule is to give the first dose of Rotarix^TM to all infants at 6 weeks of age at the same time as giving Penta1 and OPV1, and give the second dose at 10 weeks at the same time as Penta2 and OPV2.

3.4.2  Storage and effectiveness of Rotarix^TM

Rotarix^TM is a freeze-sensitive vaccine that must be stored in the refrigerator at a temperature of between +2^oC to +8^oC. It is a very safe vaccine, which provides 90–100% protection from severe rotavirus disease to fully immunized infants, and 74–85% protection against rotavirus diarrhoea of any severity.

You will receive instructions on the contraindications for giving rotavirus vaccine, and the management of possible adverse events following immunization, when Rotarix^TM is introduced into the EPI in Ethiopia.

3.5  Yellow fever vaccine

Finally, we will briefly mention an antiviral vaccine that is not part of the routine EPI in Ethiopia, but is given in certain circumstances. Yellow fever vaccine is a live-attenuated antiviral vaccine, supplied as a powder which must be reconstituted with the appropriate diluent before use. It is not included in the national EPI in Ethiopia because the risk is very low, but it is given to people who want to travel abroad to countries like Kenya and Uganda where yellow fever is endemic. Some countries (like the USA and South Africa) require a current yellow fever vaccination certificate as a condition of entry from Ethiopia. Yellow fever is a viral vector-borne disease, transmitted by certain species of mosquitoes when they take a blood meal. Infection can result in a high fever, nausea and internal bleeding leading to shock, and in extreme cases, death.

Mild reactions to yellow fever vaccine occur occasionally and include headache, muscle pain or low-grade fever.

3.6  In conclusion

Table 3.5 summarises the current and forthcoming antiviral EPI vaccines in Ethiopia.

Summary of Study Session 3

In Study Session 3, you have learned that:

1. The common antiviral vaccines in the EPI in Ethiopia are hepatitis B (HepB) vaccine, which is given in the pentavalent vaccine, oral polio vaccine (OPV) and measles vaccine. A rotavirus vaccine (Rotarix^TM) to protect against diarrhoea and dehydration caused by rotaviruses will become part of the EPI soon.
2. To guarantee long-term protection, all recommended doses of the antiviral vaccines should be given. If a child misses the scheduled date for an immunization, the child should be given the missed dose as soon as possible. There is no need to restart the immunization schedule.
3. The antiviral EPI vaccines are very effective and safe for children, and any adverse events following immunization are usually mild and easily managed; serious adverse events are extremely rare.
4. There are no contraindications to prevent giving the oral polio vaccine; if a child vomits a dose, give a replacement dose immediately; if the child has diarrhoea at the time of vaccination, give a fifth dose at least 4 weeks after the scheduled fourth dose.
5. Contraindications for the other antiviral vaccines are high-grade fever, or a severe allergic reaction or encephalopathy following a previous dose.
6. Vitamin A drops should be routinely given at the same time as measles vaccine, or if a child presents with measles, to reduce the risk of eye damage which can be serious enough to cause blindness.
7. Yellow fever vaccine is not part of the EPI in Ethiopia, but may be required by travellers going abroad to certain countries.

Self-Assessment Questions (SAQs) for Study Session 3

Now that you have completed this study session you can assess how well you have achieved its Learning Outcomes by answering the following questions. Some of the question test the Learning Outcomes for Study Session 2, as well as those for Study Session 3. Write your answers in your Study Diary and discuss them with your Tutor at the next Study Support Meeting. You can check your answers with the notes on the Self-Assessment Questions at the end of this Module.