Vaccine ingredients

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Graphic from the World Health Organization describing the main ingredients typically in vaccines WHO EN Vaccines Topic Two Ingredients static 8Dec2020.jpg
Graphic from the World Health Organization describing the main ingredients typically in vaccines

A vaccine dose contains many ingredients (stabilizers, adjuvants, residual inactivating ingredients, residual cell culture materials, residual antibiotics and preservatives) very little of which is the active ingredient, the immunogen. A single dose may have merely nanograms of virus particles, or micrograms of bacterial polysaccharides. A vaccine injection, oral drops or nasal spray is mostly water. Other ingredients are added to boost the immune response, to ensure safety or help with storage, and a tiny amount of material is left-over from the manufacturing process. Very rarely, these materials can cause an allergic reaction in people who are very sensitive to them.

Contents

Volume

Multi-dose vaccine in a vial, prepared for injection by syringe Szczepionka strep pneu.jpg
Multi-dose vaccine in a vial, prepared for injection by syringe

The volume of a vaccine dose is influenced by the route of administration. While some vaccines are given orally or nasally, most require an injection. Vaccines are not injected intravenously into the bloodstream. Most injections deposit a small dose into a muscle, but some are given superficially just under the skin surface or deeper beneath the skin. [1]

Fluenz Tetra, a live flu vaccine for children, is administered nasally with 0.1ml of liquid sprayed into each nostril. The live typhoid vaccine, Vivotif, [2] and a live adenovirus vaccine, licensed only for military use, both come as hard gastro-resistant tablets. [3] The Sabin oral live polio vaccine is taken as two 0.05ml drops of a bitter salty liquid that was historically added to sugar cubes when given to young children. [4] Rotarix, a live rotavirus vaccine, has about 1.5ml of liquid containing 1g of sugar to make it taste better. [5] The Dukoral cholera vaccine comes as a 3ml suspension along with 5.6g of effervescent granules, which are mixed and added to around 150ml water to make a sweet raspberry flavoured drink. [6]

At the other end of the volume scale, the smallpox vaccine is a minuscule 0.0025ml droplet that is picked up when a bifurcated needle is dipped into a vial containing around 100 doses. This needle is pricked 15 times into a small area of skin, just firmly enough to produce a drop of blood. [7] A little larger is the BCG tuberculosis vaccine, which is 0.05ml for babies and children under 12, and 0.1ml for others. This tiny dose is inserted a couple of millimetres under the skin, producing a small blanched blister. [8] Many vaccines for intramuscular injection have 0.5ml liquid, though a few have 1ml. [lower-alpha 1]

Some vaccines come with the active ingredients already suspended in solution and the syringe pre-filled (e.g., Bexsero meningococcal Group B vaccine [10] ). Others are supplied as a vial of freeze-dried powder, which is reconstituted prior to administration using a dilutant from a separate vial or pre-filled syringe (e.g., MMR vaccine [13] ). Infanrix hexa, the 6-in-1 vaccine that protects against six diseases, uses a combination approach: the Hib vaccine in the powder and DTPa-HBV-IPV in suspension. [9] Alternatively two separate vaccine solutions are mixed just before administration (ViATIM hepatitis A and typhoid vaccine). [19]

Immunogens

Many vaccines developed in the 20th century contain whole bacteria or viruses, which are either inactivated (killed), attenuated (weakened) or a strain chosen to be harmless in humans. Since these are so small, even a tiny amount of them contains a huge number of individuals. [21]

With bacterial vaccines, we can enumerate this with an approximate number of bacteria cells. The live typhoid vaccine contains two billion viable cells of Salmonella enterica subsp. enterica serovar Typhi, which have been attenuated and cannot cause disease. [2] The cholera vaccine has over thirty billion of each of four strains of Vibrio cholerae , which are inactivated by heat or formalin. [6] The BCG vaccine, infant dose, contains between 100,000 and 400,000 colony-forming unit of live attenuated Mycobacterium bovis . [8]

One way to count viruses is to observe their impact on host cells in tissue cultures. The two tablets of adenovirus vaccine, one with adenovirus type 4 and the other with type 7, each contain 32,000 tissue-culture infective doses (104.5 TCID50). [3] The current live polio vaccine contains two serotypes of poliovirus: over 1 million tissue-culture infective doses (106 TCID50) of type 1 and over 630,000 (105.8 TCID50) of type 3. [4] The smallpox vaccine contains between 250,000 and 1,250,000 plaque forming units of live vaccina virus per dose. [7] The MMR vaccine contains 1,000 TCID50 measles, 12,500 TCID50 mumps and 1,000 TCID50 rubella live attenuated viruses. [13]

Many modern vaccines are made of only the parts of the pathogen necessary to invoke an immune response (a subunit vaccine) for example just the surface proteins of the virus, or only the polysaccharide coating of a bacterium. Some vaccines invoke an immune response against the toxin produced by bacteria, rather than the bacteria itself. These toxoid vaccines are used against tetanus, diphtheria and pertussis (whooping cough). If the bacteria polysaccharide coating produces only a weak immune response on its own, it may be combined with (carried on) a protein that does provoke a strong response, which in turn improves the response to the weaker component. Such conjugate vaccines, may make use of a toxoid as the carrier protein. [21] For all these, the quantity of immunogen is given by weight and sometimes expressed as international units (IU). The HVP vaccine contains 120 micrograms of the L1 capsid proteins from four types of human papillomavirus . [15] The pneumococcal conjugate vaccine contains 32 micrograms of pneumococcal polysaccharide conjugated with CRM197 (a diphtheria toxin). [11]

Another variant is the RNA vaccine, which contains mRNA embedded in lipid (fat) nanoparticles. The mRNA instructs body's own cell machinery to produce the proteins that stimulate the immune response. [21] Comirnaty, the Pfizer-BioNTech COVID-19 vaccine contains thirty micrograms of BNT162b2 RNA. [22]

Excipients

Excipients are substances present in the vaccine that are not the principal immunological agents. These may be present to enhance the vaccine's potency, ensure safety, aid with storage or are left over from the manufacturing process. [23]

Adjuvants

Live vaccines produce a strong immune response that lasts a long time, but they are not suitable for people with weakened immune systems. Other kinds of vaccine, where the pathogen has been inactivated or that contain only part of the pathogen, often alone produce a weaker response and require booster doses. In these vaccines, a substance called an adjuvant is added to make the immune response stronger and longer lasting. [21] [24]

The most commonly used adjuvants are aluminium salts such as aluminium hydroxide, aluminium phosphate or potassium aluminium sulphate (also simply called alum). [24] [25] These aluminium salts can be responsible for soreness and redness at the vaccination site but do not cause any long-term harm to human health. The amount of aluminium in these vaccines ranges from 0.125 milligrams in the pneumococcal conjugate vaccine to 0.82 milligrams in the 6-in-1 vaccine. The Meningococcal Group B vaccine contains 0.5 milligrams and in the UK Immunisation Schedule is given at the same time as the 6-in-1 vaccine at eight and sixteen weeks, giving a combined dose of 1.32 milligrams of aluminium. Aluminium salts are commonly and naturally consumed in small quantities, and the quantity in this combined vaccine dose is lower than the weekly safe intake level. [25] Vaccines containing aluminium adjuvants cannot be frozen or allowed to freeze accidentally in a refrigerator, as this causes the particles to coagulate and damages the antigen. [26]

Another adjuvant used in some flu vaccines is an oil-in-water emulsion. The oil, squalene, is found in all plant and animal cells, and is commercially extracted and purified from shark liver. The flu vaccine for older adults, Fluad, uses an adjuvant branded MF59, which has squalene (9.75 milligrams), citric acid (0.04 milligrams) and three emulsifiers: polysorbate 80, sorbitan trioleate, sodium citrate (1.175, 1.175 and 0.66 milligrams respectively). [27] The H1N1 swine-flu vaccine, Pandemrix, used the adjuvant branded AS03, which has squalene (10.69 milligrams), DL-α-tocopherol (11.86 milligrams) and polysorbate 80 (4.86 milligrams) [28]

Preservatives

Preservatives prevent the growth of bacteria and fungi, and are more commonly used in vaccines produced as multi-dose vials. They must also be non-toxic in the dose used and not adversely affect the immunogenicity of the vaccine. [29] Thiomersal is the best known and most controversial preservative. It was phased out of UK vaccines between 2003 and 2005 and is not used in any routine vaccines in the UK. As a precaution, the US and Europe have also removed thiomersal from vaccines, despite there being no evidence of harm. [25] The US-licensed vaccines in the routine paediatric schedule generally have no thiomersal at all; a few have only a trace amount as a residual from manufacturing (less than one microgram). This is also the case for influenza vaccines in the US that come in single-dose vials or prefilled syringes. Some influenza vaccines are also available as a multi-dose vial, and in that form contain thiomersal (24.5 micrograms of mercury). [30]

Phenol 0.25% v/v is used in Pneumovax 23, a pneumococcal polysaccharide vaccine, and in the smallpox vaccine. However, phenol reduces the potency of diphtheria and tetanus toxoid-containing vaccines. Similarly, thiomersal weakens the immunogenicity of the inactivated poliovirus vaccine, so the IPOL vaccine contains 2–3 microlitres of 2-phenoxyethanol instead. [31] [32]

Stabilisers

Stabilisers protect the vaccine from the effects of temperature and ensure it does not degrade in storage. For vaccines that are freeze-dried, they provide a necessary bulk. Without them, the vaccine powder would be invisibly tiny (ranging from nanograms to a few tens of micrograms) and stick to the vial glass. Stabilisers used for vaccines include sugars (sucrose, lactose), sorbitol, amino acids (glycine, monosodium glutamate) and proteins (hydrolysed gelatin). There have very rarely (one in two million vaccinations) been cases of allergic reaction to the proteins in gelatin. [25] [33] The source of gelatin, pork, is of religious concern to Jewish and Muslim communities, though some leaders have ruled this is not a cause to reject vaccines that are injected or inhaled rather than ingested. There are alternatives for some vaccines that contain gelatine. [25] [34]

Acidity regulators such as phosphate salts keep the pH within a required range during manufacture and in the final product. Other salts help ensure the vaccine is isotonic with body fluids. [35]

Manufacturing residuals

There are materials that serve no function in the final vaccine but are left over from the manufacturing process. Bacteria and viruses may be inactivated using formaldehyde. The quantity remaining in diphtheria or tetanus toxoid vaccines licensed in the US is required to be less than 0.1 milligrams (0.02%). Although formaldehyde has potentially toxic and carcinogenic properties in large doses, it is present in the blood (due to natural biochemical processes) at much higher concentrations than permitted in vaccines. Alternatives used in some vaccines include glutaraldehyde and β-propiolactone. Antibiotics may be used to prevent bacteria growing during vaccine manufacture and traces of these may remain. Antibiotics that some people are allergic to (such as cephalosporins, penicillins and sulphonamides) are not used. Those that are used include kanamycin, gentamicin, neomycin, polymyxin B, and streptomycin. [25] [36]

A small amounts of protein may remain from the material used to grow viruses, to which some people may be hypersensitive. Some influenza and yellow fever vaccines are grown in chicken eggs, and measles or mumps vaccines may be grown in chick embryo cell culture. Engerix-B, a recombinant DNA vaccine for hepatitis B is produced in yeast and may contain up to five percent yeast protein. [36] Cervarix, an HPV vaccine, is grown in a cell line from the cabbage looper moth. [37] The amount of insect protein remaining is less than forty nanograms. [36]

Some components of the vaccine vial or syringe may contain latex rubber. This is a problem for those with a severe allergic reaction to latex, but not for those who get contact dermatitis after wearing latex gloves. [25] [38]

Notes

Related Research Articles

<span class="mw-page-title-main">Vaccine</span> Pathogen-derived preparation that provides acquired immunity to an infectious disease

A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as a threat, destroy it, and recognize further and destroy any of the microorganisms associated with that agent that it may encounter in the future.

<span class="mw-page-title-main">Thiomersal</span> Organomercury antiseptic and antifungal agent

Thiomersal (INN), or thimerosal, also sold under the name merthiolate is an organomercury compound. It is a well-established antiseptic and antifungal agent.

<span class="mw-page-title-main">Influenza vaccine</span> Vaccine against influenza

Influenza vaccines, colloquially known as flu shots, are vaccines that protect against infection by influenza viruses. New versions of the vaccines are developed twice a year, as the influenza virus rapidly changes. While their effectiveness varies from year to year, most provide modest to high protection against influenza. Vaccination against influenza began in the 1930s, with large-scale availability in the United States beginning in 1945.

<span class="mw-page-title-main">H5N1 vaccine clinical trials</span> Clinical trials of influenza vaccine

H5N1 clinical trials are clinical trials concerning H5N1 vaccines, which are intended to provide immunization to influenza A virus subtype H5N1. They are intended to discover pharmacological effects and identify any adverse reactions the vaccines may achieve in humans.

Cervarix is a vaccine against certain types of cancer-causing human papillomavirus (HPV).

<span class="mw-page-title-main">Hepatitis A and B vaccine</span> Vaccine against hepatitis virus A and B

Combined hepatitis A and B vaccine, is used to provide protection against hepatitis A and hepatitis B. It is given by injection into muscle.

Pharmaceutical formulation, in pharmaceutics, is the process in which different chemical substances, including the active drug, are combined to produce a final medicinal product. The word formulation is often used in a way that includes dosage form.

In immunology, an adjuvant is a substance that increases or modulates the immune response to a vaccine. The word "adjuvant" comes from the Latin word adiuvare, meaning to help or aid. "An immunologic adjuvant is defined as any substance that acts to accelerate, prolong, or enhance antigen-specific immune responses when used in combination with specific vaccine antigens."

<span class="mw-page-title-main">Hepatitis B vaccine</span> Vaccine against hepatitis B

Hepatitis B vaccine is a vaccine that prevents hepatitis B. The first dose is recommended within 24 hours of birth with either two or three more doses given after that. This includes those with poor immune function such as from HIV/AIDS and those born premature. It is also recommended that health-care workers be vaccinated. In healthy people, routine immunization results in more than 95% of people being protected.

<span class="mw-page-title-main">Hepatitis A vaccine</span> Vaccine to prevent hepatitis A

Hepatitis A vaccine is a vaccine that prevents hepatitis A. It is effective in around 95% of cases and lasts for at least twenty years and possibly a person's entire life. If given, two doses are recommended beginning after the age of one. It is given by injection into a muscle. The first hepatitis A vaccine was approved in Europe in 1991, and the United States in 1995. It is on the World Health Organization's List of Essential Medicines.

<span class="mw-page-title-main">Pandemrix</span> Flu vaccine

Pandemrix is an influenza vaccine for influenza pandemics, such as the 2009 flu pandemic. The vaccine was developed by GlaxoSmithKline (GSK) and patented in September 2006.

<span class="mw-page-title-main">Tick-borne encephalitis vaccine</span> Vaccine against tick-borne encephalitis

Tick-borne encephalitis vaccine is a vaccine used to prevent tick-borne encephalitis (TBE). The disease is most common in Central and Eastern Europe, and Northern Asia. More than 87% of people who receive the vaccine develop immunity. It is not useful following the bite of an infected tick. It is given by injection into a muscle.

A subunit vaccine is a vaccine that contains purified parts of the pathogen that are antigenic, or necessary to elicit a protective immune response. Subunit vaccine can be made from dissembled viral particles in cell culture or recombinant DNA expression, in which case it is a recombinant subunit vaccine.

<span class="mw-page-title-main">2009 swine flu pandemic vaccine</span> Protection against the H1N1/09 virus

The 2009 swine flu pandemic vaccines were influenza vaccines developed to protect against the pandemic H1N1/09 virus. These vaccines either contained inactivated (killed) influenza virus, or weakened live virus that could not cause influenza. The killed virus was injected, while the live virus was given as a nasal spray. Both these types of vaccine were produced by growing the virus in chicken eggs. Around three billion doses were produced, with delivery in November 2009.

Hepatitis A and typhoid vaccine is a combination vaccine to protect against the infectious diseases hepatitis A and typhoid. It is a combination of inactivated Hepatitis A virus and Vi polysaccharide of Salmonella typhi bacteria. Branded formulations include Hepatyrix from GlaxoSmithKline, and ViVaxim and ViATIM from Sanofi Pasteur.

CoviVac is an inactivated virus-based COVID-19 vaccine developed by the Chumakov Centre, which is an institute of the Russian Academy of Sciences. It was approved for use in Russia in February 2021, being the third COVID-19 vaccine to get approval in Russia. It obtained a permission for phase III clinical trial on 2 June 2021.

<span class="mw-page-title-main">Sanofi–GSK COVID-19 vaccine</span> Vaccine candidate against COVID-19

The Sanofi–GSK COVID-19 vaccine sold under the brand name VidPrevtyn Beta, is a COVID-19 vaccine developed by Sanofi Pasteur and GSK.

<span class="mw-page-title-main">Corbevax</span> Vaccine against COVID-19

Corbevax is a protein subunit COVID-19 vaccine developed by Texas Children's Hospital Center for Vaccine Development and Baylor College of Medicine in Houston, Texas and Dynavax technologies based in Emeryville, California. It is licensed to Indian biopharmaceutical firm Biological E. Limited (BioE) for development and production.

<span class="mw-page-title-main">Vaccine wastage</span>

Vaccine wastage is the number of vaccines that have not been administered during vaccine deployment in an immunization program. The wastage can occur at multiple stages of the deployment process, and can take place in both unopened and opened vials, or in oral admission. It is an expected part of vaccination deployment and is factored into the manufacturing process.

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Works cited

  • Garçon, Nathalie; Friede, Martin (2018). "Chapter 6: Evolution of Adjuvants Across the Centuries". In Plotkin, Stanley A.; Orenstein, Walter A.; Offit, Paul A. (eds.). Plotkin's vaccines (Seventh ed.). Philadelphia, PA. ISBN   9780323357616.{{cite book}}: CS1 maint: location missing publisher (link)
  • Finn, Theresa M.; Egan, William (2018). "Chapter 7: Vaccine Additives and Manufacturing Residuals in Vaccines Licensed in the United States". In Plotkin, Stanley A.; Orenstein, Walter A.; Offit, Paul A. (eds.). Plotkin's vaccines (Seventh ed.). Philadelphia, PA. ISBN   9780323357616.{{cite book}}: CS1 maint: location missing publisher (link)