Immunisation Masterclass 1 - Why Vaccinate?
By Pasha Yuen
Immunisation Masterclass (1) – Why Vaccinate?
Get Vaccinated!
National Immunisation Awareness Month is an annual campaign, aiming to raise awareness of the public the importance of vaccination. General awareness of the importance of vaccination has increased substantially following the COVID-19 pandemic. In the UK, the NHS has established an Immunisation Schedule which reminds people when to get a compulsory vaccination, and what optional vaccinations are available.
Several changes have been implemented in recent years, to ensure people are having the vaccinations they needed. For example, in September 2019, Human Papillomavirus (HPV) vaccinations have been extended to both girls and boys aged 12 to 13 years old.
During the COVID-19 pandemic, the UK NHS issued several “Vaccine Updates” regarding the evolving state of the pandemic, including the implementation of the step-by-step COVID-19 vaccination programme in 2021 based on associated risk with different groups (e.g., age, health conditions, occupational group at higher risk of exposure) and booster vaccination programme against various COVID-19 variants.
Other changes have also been implemented during the pandemic; the neonatal Bacillus Calmette-Guérin (BCG) immunisation programme in 2022, and a new vaccine available for the shingles immunisation programme in 2023.
Recently, the UK’s Health Security Agency has announced the Respiratory Syncytial Virus (RSV) Immunisation Programme. Starting from the 1st of September 2024, people aged 75 to 79 years old, or women who are at least 28 weeks pregnant, are eligible for a single dose of RSV vaccine. Check the NHS website for monthly updates information on the national immunisation programme.
Vaccines and Immunisation
Vaccines are a preventive measure against certain diseases. The usual way of making them is to synthesise tiny amounts of specific parts of the pathogen, such as inactivated viruses that have either been killed or are in a weakened form. These pathogen components are attached to a backbone structure, usually one that has been tried and tested for many years, and formulated into a vaccine that can be administered. The most common route of administration is by injection, either intramuscularly or subcutaneously. In some cases, vaccines can also be given intranasally or orally, depending on the desired site of immunity.
The body will recognise the tiny amounts of pathogen in the vaccine, which will trigger an immune response so that antibodies can be produced against these components. During this immune response there may be a fever, which is a normal reaction to vaccination and does not mean the inactivated components have caused any infection.
Upon being exposed to the same components of this pathogen during an actual bacterial or viral infection in the future, our immune cells would immediately recognise the invading pathogen as they have already been exposed to it during vaccination. This prevents the normal delay while the body works out how to fight the infection. Vaccination helps the immune system to “remember” the pathogens, and thus be able to produce the corresponding antibodies quickly to fight the infection. This can mean the pathogen is cleared by the immune system without the infected individual even realising, or the infection may be much less severe and clear much more quickly than it would have without vaccination.
You can learn more about vaccines on the WHO website: Vaccines and immunization: What is vaccination? (who.int)
The Importance of Vaccination
The aim of vaccination is to help you develop immunity against fatal or serious diseases. In addition to protecting yourself, having a vaccine will also help stop the spread of diseases. Having enough people vaccinated can help to develop herd immunity.
Herd immunity is when the proportion of a population with immunity against a disease is large enough to prevent infection from spreading in that population. This can benefit everyone, but it is particularly important in protecting those with weakened immune systems, who would not have been able to receive a vaccination or who may have not mounted a sufficient immune response. Such people include those born with congenital immune system disorders, those on chemotherapy, and those who are pregnant, where the outcome of infection could be extremely severe or even fatal. By vaccinating the majority of the population we can reduce the risk of those people being exposed to the infection.
Vaccine successes
Smallpox was a deadly disease which was fatal in 30% of the cases. With a global joint effort, an immunisation plan of smallpox was launched by the WHO in 1967, and 20 years later, by 1980, smallpox became the first disease to be globally eradicated. Another example of a successful vaccination campaign is Polio, which was eliminated in the UK in the 80s. By comparing the rate of disease prevalence with vaccine availability, we can observe a decreasing trend of people being infected. We most recently observed this during the COVID-19 pandemic.
Vaccine Safety and Signal Evaluation
Monitoring the safety profile of vaccines is very specialised and differs from the monitoring for other products. This is partly due to the way vaccines are manufactured, making the batch number much more important than it might be for other products, and also because they are given to healthy individuals to provoke immune responses in the absence of any illness, making the benefit-risk profile a key consideration.
Health authorities in different countries have their own vaccine safety surveillance plans, with various systems for signal reporting and evaluation. In the following blogs in this series, we will explore the safety considerations for each of the vaccine categories.
Stay tuned for our next blog of the immunisation masterclass, in which we will cover the topic of oral vaccines, what are they for, why choose oral administration over injection, and the safety profile of oral vaccines.
Please click here to read the 2nd Masterclass in the series “Oral Vaccines – What are they ?”
Reference
Smallpox : a history / S.L. Kotar and J.E. Gessler. | Wellcome Collection
UK aid to help vaccinate more than 400 million children a year against polio – GOV.UK (www.gov.uk)
Immunisation Masterclass 2 - Oral Vaccines - What are they ?
By Pasha Yuen
Oral Vaccines
When talking about vaccines, the first thing that comes to your mind may be getting an injection. However, some vaccines can be administered through an oral route instead. There are currently oral vaccines available to protect against several serious conditions including poliomyelitis (“polio”), cholera, rotavirus, and typhoid.
There are many advantages of oral administration compared with injection for vaccination. These include ease of administration without the use of needles, which requires less training for the healthcare providers and also reduces cost; no risk of injection site reactions; easier storage, since many injectable vaccines need to be stored at a low temperature; and speed, as oral vaccines can be quickly administered, which means more people can be vaccinated in each clinic.
The first oral vaccine proven to be effective was the oral polio vaccine (OPV). In the UK Polio vaccines are normally administered as injections to babies as part of the 6-in-1 vaccine, 4-in-1 (DTaP/IPV) pre-school booster, and the 3-in-1 (Td/IPV) teenage booster. Although there are no confirmed cases of polio infection in the UK since 1984, it is important to continue to immunise against this devastating condition to prevent another outbreak. Up to 75% of cases are asymptomatic, making polio extremely contagious, with 1 in 200 infections leading to irreversible paralysis. Between 5-10% of those paralysed die due to their breathing muscles becoming immobilised. Vaccinations have ensured that polio is mostly eradicated worldwide, following a global effort led by the World Health Organization, however there are still pockets of this virus in some regions of the world. As described in the first blog of this series, herd immunity can protect those who are unvaccinated, including those who are unable to receive vaccines due to specific health conditions that affect the immune system.
The UK NHS immunisation programme also includes 2 doses of oral rotavirus vaccine for all infants at 8 and 12 weeks old, except those who have severe combined immunodeficiency (SCID). This protects children from rotavirus, a highly transmissible pathogen that can cause diarrhoea and vomiting, which can be severe and even life-threatening in children. (Rotavirus vaccine – NHS [www.nhs.uk])
How does oral vaccination work?
Oral vaccines are swallowed, therefore they are administered directly into the gastrointestinal (GI) tract, targeting the gut-associated lymphoid tissue (GALT). This triggers a gut-based mucosal immune response.
Immunity in the gut is managed by dendritic cells and specialised M cells, which capture antigens and present them to the T cells for the subsequent immunity cascade. This cascade includes T cell and B cell differentiation, followed by generation of Immunoglobulin A (IgA). Secretory IgA is the type of antibody found in mucous secretions, which protects the body from pathogens entering via the gut (such as polio, rotavirus etc). Injection-based vaccines induce the production of IgG, which is responsible for a systemic (throughout the body and in the bloodstream) immune response rather than locally in the gut. Therefore, oral vaccines are needed where a specific gut protective effect is required. Secretory IgA in GALT is particularly important, due to its ability to block pathogens from adhering to mucosal surfaces.
Oral Vaccines – Challenges and Clinical Trials
Not everyone can be vaccinated using the currently available oral vaccines. For example, the oral version may contain an inactivated version of the virus, which may mutate in the body and become active lower down in the gastrointestinal tract. This would not cause a problem for the vaccinated individual as they will have mounted the immune response by then. But people with immune system disorders, or with carers who are not immune to the condition, may require a killed version of the virus, or an injection with specific parts of the pathogen. This is why some injectable versions are still required despite the advantages of oral vaccines.
Administration of vaccines through the oral route in general have a lower bioavailability, due to the degradation of antigens when entering the stomach and the intestine. Therefore, some of the obstacles in designing an oral vaccine include the resistance against the highly acidic environment in the stomach and the effect of digestion, which require having a higher level of antigens. In current years, efforts are still being made to improve the effectiveness and safety of currently available oral vaccines, for example a novel OPV clinical trial in Panama. (Study Details | Study of a Novel Type 3 Oral Poliomyelitis Vaccine in Panama | ClinicalTrials.gov)
In addition to the already available oral vaccines, clinical trials investigating oral vaccines against other pathogens are also taking place. A Phase II study completed in 2018 investigated the efficacy of oral H1N1-based influenza vaccine, which showed a promising result in terms of efficacy and safety. (Efficacy, immunogenicity, and safety of an oral influenza vaccine: a placebo-controlled and active-controlled phase 2 human challenge study – PubMed (nih.gov))
In the future, development of effective oral vaccines could be incredibly helpful in healthcare. Want to learn more on vaccination? Read the next blog in this series on seasonal vaccines!
Reference
Recent development of oral vaccines (Review) – PMC (nih.gov)
Oral Vaccines: A Better Future of Immunization – PMC (nih.gov)
Immunisation Masterclass 3 - HPV Vaccination
By Pasha Yuen
International HPV Awareness Day, observed annually on 4th March, serves as a crucial initiative to enhance public understanding of human papillomavirus (HPV). This global campaign aims to educate individuals about what HPV is, the risks associated with the virus, and the preventive measures that can be taken to curb its spread. By raising awareness, the day encourages informed decision-making, promotes vaccination, and highlights the importance of regular screenings in preventing HPV-related diseases.
Introduction to HPV
Human Papillomavirus (HPV) is a common virus with over 100 subtypes. It can be spread through sexual activity; through penetrative intercourse or skin-to-skin genital contact. Whilst most HPV subtypes are harmless and classified as low-risk, some high-risk HPVs are associated with serious health conditions – including cervical, anal and throat cancers, and also genital warts. The subtypes HPV 16 and HPV 18 account for over 70% of HPV-associated cervical cancer cases in women, and over 80% of HPV-associated oropharynx (throat) cancer in men. The table below summaries the HPV subtypes and disease associated with them (Burd, 2003).
Amongst all HPV-related cancers, cervical cancer is the most common. 99% of cervical cancer cases are associated with chronic HPV infection. Women between the ages of 18 to 30 are more prone to HPV infection. However, cervical cancer typically develops later, often after the age of 35, highlighting the slow progression of the disease. Whilst cervical cancer remains one of the leading causes of cancer-related deaths worldwide, in the UK, the 10-year survival rate is up to 86.8%. Encouragingly, most cervical cancer cases are preventable through early detection and vaccination (Cervical cancer statistics | Cancer Research UK). To learn more about cervical cancer protection, read our blog on cervical screening!
Who should get the HPV vaccine?
In the UK, the routine adolescent and universal HPV vaccination programme has been available since 2008 and expanded to include males in 2019. School children who are in school Year 8 (around 11 to 13 years old), are eligible for one dose of HPV vaccine, which is paid for by the UK National Health Service (NHS). Even if you missed the dose in school, you will still be eligible until your 25th birthday – so contact your GP today if you live in the UK and have not received your HPV vaccine yet!
In addition to the vaccination programme for school age children, a vaccination programme is also available in the UK for all males who have sex with men. Those under the age of 25 require only one dose, whereas men aged 25 and above should receive two doses for optimal protection.
The Importance of HPV Vaccination
Vaccination is understood to be an effective preventive measure against infectious diseases such as influenza and, more recently, COVID-19; but what exactly does the HPV vaccine do? Whilst most HPV subtypes are not harmful, the vaccine protects against high-risk HPV strains that can cause cancer.
In the UK, Gardasil 9 is used for protection against HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58. Since the introduction of the immunisation programme, HPV vaccine coverage (first dose) has reached 77% in female and 71% in male. This has led to a significant reduction in cervical cancer cases. A UK-based joint study reported an 83.9% reduction of cervical cancer rates when comparing a vaccinated cohort and a reference cohort of people who have never received HPV vaccination. As cervical cancer is a fatal condition if it is not caught and treated early enough, these vaccinations have saved countless lives.
Common Myths about HPV Vaccination
Myth #1 – Is it safe?
One of the most common concerns regarding HPV vaccines is the lack of safety data as it is perceived as a newly developed vaccine. Whilst the established history of HPV vaccination might not be as long as flu vaccines, HPV vaccines have been used for over a decade worldwide and have a very well-documented safety profile.
The most common adverse events or side effects are injection site reaction, such as pain, redness, or swelling in the arm, or mild vaccine-related systemic reactions, for example dizziness, nausea, and headache. Severe allergic reactions are extremely rare, occurring in only three cases per one million vaccinated individuals. Extensive clinical trials have been conducted to ensure the safety of the vaccine, before being granted approval from health care authorities such as the FDA or the EMA. Effort has also been made for post-marketing surveillance to ensure safety, allowing the public to report any side effects. Since HPV vaccine has been marketed, there have been millions of people protected from all the risks associated with infection, and only 7 fatal cases have been reported, none of which were considered related to the vaccine.
Myth #2 – Only female needs vaccination
Although cervical cancer is the most well-known HPV-related cancer, men are also at risk of developing HPV-related cancers, such as throat, penile, and anal cancer. Apart from the risk of developing cancer themselves, they can also act as a virus carrier and spread it to other people. Since HPV is spread through sexual intercourse, vaccinating both men and women is essential to achieving herd immunity and reducing the overall prevalence of the virus.
Steps to Take for HPV Awareness Day
As International HPV Awareness Day approaches, taking proactive steps can make a meaningful difference in the fight against HPV. By ensuring vaccinations are up to date and sharing accurate information, we can help reduce stigma, dispel misconceptions, and protect future generations from HPV-related diseases. Small actions, such as having conversations with loved ones or promoting awareness within your community, can contribute to a healthier, more informed society. Let’s work together to spread knowledge and prevention, one step at a time!
