It's been half a year since we have been grappling with this new Zoonotic infection. Our knowledge of how this virus affects the human body has increased significantly. What is not so clear however is what factors lead to one person developing complicated disease while another person with similar baseline risk factors escapes unscathed. Surely there are factors in play in addition to pure luck, but are there any actions which could be taken to boost the immune system ?
One observation which has been replicated in various countries is that children fare better than adults. Risk of complicated disease appears to increase linearly with age, unlike influenza which has a U shaped curve ( peaking in the very young and very old). One theory which has been postulated and is currently being tested is whether innoculation with live attenuated ( weakened ) vaccines such as BCG and MMR boosts the innate immune system and effects response to SARS-COV2 exposure. Studies are ongoing in UK, USA, Australia and Holland to investigate this in context of BCG vaccine and more recently MMR vaccine has been highlighted for similar reasons.
Allow me to summarise the immune system for you. This is the army of defenders we have within our bodies who protect us from attackers. For the purpose of simplification, our immune system can be divided into a early / general / frontline system called ‘innate’ and a late / specialized / higher command system called ‘adaptive’. I will illustrate the entry of a foreign pathogen and how our body responds to it. It is postulated that live weakened vaccines such as BCG and perhaps MMR strengthen the innate arm of immune system in contrast to a specific vaccines which only work on the adaptive arm. The immune modulatory properties of BCG vaccine is also utilised for treatment of bladder and skin cancer.
INNATE IMMUNE SYSTEM:
Once a foreign invader such as virus, bacteria or fungi is present in the body, the immune system gets to work to flush it out. Here is a sequence of events on how this happens
1. Macrophages : These are the security guards of the system patrolling the tissues of our body. They identify foreigners and mount an inflammatory response. On one hand they start gobbling up and breaking down the intruders and on the other hand, express chemical messages to get more macrophages and neutrophils into the fight. When they have broken up the pathogen, they present the peices on their surface for the benefit of other defence response cells joining the fight.
2. Neutrophils: These are kamikaze fighters who are present in the blood stream. Once they receive messages from macrophages in the tissue, they pass through blood vessels into tissues to join the battle.This is a one way route and neutrophils do not survive the fight. They have an average life of five days once starting battle and die during the effort.... turning into 'pus' afterwards.
3. Dendritic Cells: These are messenger cells which connect the non specific first defence innate system with the more specialized adaptive arm of immune system. They travel up lymph channels into lymph nodes. Here they present the antigen to T Cells and B Cells. We have lymph nodes around our neck, armpits and groins, and this is why they swell up as a reaction to infection. Like Macrophages, these are also ‘Antigen Presenting Cells’.
ADAPTIVE IMMUNE SYSTEM
Within lymph nodes the message from dendritic cell is first received by Naive T Cells. Depending upon the response required, there are generally any number of three pathways that this Naive T Cell can pursue next to defeat the pathogen invader.
1. Humeral Response: T Cells activate B Cells to convert them to plasma cells and produce antibodies specific against the antigen. These antibodies, along with some B Cells travel up stream to the lymphatic thoracic duct and re-enter the blood stream. They then extravasate from blood vessels to re-enter the war zone with antibodies produced specifically against the invader. Within the lymph node some of the B cells form memory cells. There cells keep memory of the antigen and can deploy antibodies quickly in case the same pathogen attacks again. This is the mechanism by which vaccines works, deploying antibodies quickly as soon as a recognised antigen enters the body.
2. Cytotoxic Response: T Cells can also stimulate Cytotoxic T Cells. These are cells which not only eat up the pathogen, they also gobble up cells of the body which have become infected by the pathogen. Hence they sacrifice infected body cells for the greater cause of defeating the invader. This hyperactive and aggressive response can be a cause of complication for certain conditions in the later stage, such as COVID19. In severe form this may be described as part of Cytokine Storm’ and lead to clinical deterioration. It is this excessive body response which is slowed down by use of anti-inflammatory steroids and IL-6 inhibitors.
3. Upregulation of Innate system by Adaptive system: T Cells can also travel back to the site of infection and up regulate the frontline response more locally. It is like a commander moving from headquarters to fight with frontline soldiers. Once on the front lines, T Cells express more chemicals to intensify the activity of macrophages, neutrophils and dendritic cells and rally the troops. It is this part of the immune response that live attenuated vaccines are postulated to effect the most. A Danish study demonstrated that children receiving the BCG vaccine subsequently experienced 30 % fewer respiratory infection which are not related to TB. These findings were later confirmed in the British Journal of Medicine.
So does the recent use of live attenuated vaccines explain why children experience milder COVID19 symptoms? We don't really know and studies are ongoing. However there are other chains of thought as well. It could simply be the case that any kind of immune system challenge will strengthen it. Apart from children, another group of patients who appear to suffer milder disease are those living in significant unhygienic conditions.A study of homeless patients in Boston showed that among almost 200 residents of the shelter testing positive for SARS-COV2, only a single resident had symptoms ( that too mild ). It has been observed that patients living in slum dwellings appear to do better than rich ones. There may be other confounding factors in play as well including metabolic risk factors such as obesity, diabetes and raised blood pressure among the well-to-do patients. It may also be possible however that unhygienic conditions coupled with endemic TB, malaria, gut worms etc provide regular ‘match practice’ to the immune system of these poor patients, in the proces keeping their immune system fighting fit.
So what could you and I , living in our sterile bubbles do in order to challenge our immune systems ? The answer is to vaccinate yourself. Speak to your Doctor about any vaccines you may be eligible for and get these done. It may provide you more benefit that you think.
1. Flu Vaccine: This is recommended yearly to all patients above the age of six months. During a bad winter, Influenza can cause the death of up to 40,000 patients in USA. This fall it is expected that Flu and Covid19 will attack together. In addition, common symptoms of both are identical....fever, muscle pains and dry cough. During most flu vaccine campaigns, the maximum uptake we can expect is about 40 % of population receiving the vaccine. This winter the medical fraternity is hoping that many more, perhaps double the number will receive the vaccine. This will reduce incidence of Influenza, which will in turn increase hospital capacity for COVID19 patients.
2. Pneumonia vaccination: This is recommended to patients above the age of 50 and consists of a course of two injections. Prevnar13 is a conjugate vaccine administered first. This is followed up after two months with Pneumovax 23. Considering that a minority subset of patients COVID19 have complication by bacterial pneumonia, vaccinating against it certainly seems sensible.
3. MMRV, HAV & HBV: Immune status for measles, mumps, rubella, varicella, hepatitis A and hepatitis B can be checked with a simple blood test. Patients whose immune status has weakened over time then have the option of receiving a booster dose. MMRV is available in a single vial, as is HAV+HBV.
4. DTaP(IPV):A tetanus booster is usually last given at age 16 and a subsequent booster is advised every ten years. Tetanus booster is usually accompanied by Diphtheria (D) and whooping cough (aP). Patients who do not have documentation of or are not aware of their polio vaccination status may choose to receive Polio ( IPV) booster alongside as these are available in a combined vial and may be beneficial for certain patients for the purpose of work documentation.
5. Shingles: Shingrix vaccine recommended after age 50 for this condition which can lead to chronic pain.
6. Routine childhood and adolescent vaccines: It is important that children continue to be receive their routine childhood vaccinations in a timely fashion. In this context MMR ( 12 months and 4 years here ), and Varicella ( 15 months and 4 years here ) have particular importance....but all vaccinations are important. With schools closed and social isolation, we have greatly reduced the protective viral infections they are accustomed to during school going days. It is important that we do not deprive them of the other method of exercising their immune system....vaccinations.
Do not wait....Vaccinate
INFORMATION & DISCLAIMER:
I obtained my primary medical education from India and post graduate MD in Family Medicine from the United Kingdom. After working in the NHS for 15 years, I moved to Canada five years ago. As a Family Physician, my specialty is engaging patients, interpreting medical information for them, guiding them through their health journey, promoting wise health choices and encouraging early detection and management of disease. The information on this blog is accurate as per time of publishing and patients should check the main blog for updates. Scientific information and evidence changes dynamically and my opinions would change accordingly. The recommendations on this blog are not prescriptions and any patients considering these should consult with a physician to check if these are applicable to their unique case. Patient confidentiality must be upheld at all times and any patients wishing to discuss specific medical scenarios on social media are requested to do so anonymously in 'third party' sense.
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