How vaccines work
Vaccines work by teaching the immune system how to fight off a disease in case it ever comes into contact with it. This greatly reduces the risk of becoming seriously ill or spreading a disease to others. Vaccines can protect against one or multiple diseases. Sometimes, multiple vaccines may be given at once to protect against several diseases.
Vaccines can protect against either one or multiple diseases. Sometimes, multiple vaccines may be given at once to protect against several diseases.
Most vaccines contain a weakened or an inactivated form of a virus or bacterium, or a small part of it, called an antigen.
When a person gets vaccinated, their immune system recognises the antigen as foreign. This activates immune cells to produce antibodies and create a memory of the virus or bacterium.
Later, if the person comes into contact with the actual virus or bacterium, their immune system will remember it, and then produce the right antibodies and activate the right immune cells quickly, to kill the virus or bacterium. This protects the person from the disease.
In contrast, people who become immune by getting the actual disease can spread it to others and put themselves at risk of serious complications from the disease.
Protection
Different vaccines bring about different levels of protection. The duration of protection varies depending on the disease. Some vaccines can only protect against a disease for a short period and may need booster doses; for others, immunity can last a lifetime.
Vaccination not only protects people who have received a vaccine. It also indirectly protects unvaccinated people in the community, by decreasing the risk of exposure to infection. This is known as community immunity (also called herd immunity).
Components
In addition to one or more antigens, other components can also be added to help keep the vaccine stable and effective. Regulators make sure that all these components are safe.
These components include:
- stabilisers: to keep vaccine components stable;
- adjuvants: these improve the immune response to the vaccine by making the response stronger, faster and more sustained over time – an example of which is aluminium;
- excipients: these are inactive ingredients, like water, or sodium chloride (salt), as well as preservatives or stabilisers that help the vaccine remain unchanged during storage, keeping it active.
In some vaccines, there may also be trace amounts of other substances used in the manufacturing process, such as ovalbumin (a protein found in eggs) or neomycin (an antibiotic). If these substances might cause a reaction in sensitive or allergic individuals, their presence is declared in the information given to healthcare workers and patients.
Tipi ta’ vaċċini
il-vaċċini mRNA fihom molekula msejħa aċidu ribonuklejku messaġġier (mRNA) li tagħti struzzjonijiet dwar kif għandha tiġi miġġielda marda liċ-ċelloli tagħna.
Ladarba l-mRNA fil-vaċċin jidħol fiċ-ċelloli tagħna, dan jipprovdi struzzjonijiet biex jagħmel proteina li ma tagħmilx ħsara li taqbel ma’ parti mill-virus li l-vaċċin huwa mfassal biex jipproteġi kontrih.
Minħabba li l-vaċċini mRNA jagħtu struzzjonijiet biex jagħmlu biċċa żgħira minn virus, ma jistgħux jikkawżaw mard.
Wara li ċ-ċelloli tagħna jibdew jipproduċu l-proteina, is-sistema immunitarja tagħna tirrikonoxxiha bħala barranija, u tattiva ċelloli immunitarji u toħloq antikorpi. Dan il-proċess iħarreġ lis-sistema immunitarja tagħna biex tiġġieled il-viruses li fihom dik il-proteina, u dan ifisser li jekk il-ġisem jiltaqa’ mal-virus reali, ikun jista’ jiġġieled aħjar l-infezzjoni.
Il-vaċċini b’vettur virali fihom virus li ma jagħmilx ħsara li jwassal sezzjoni żgħira tal-kodiċi ġenetiku tal-virus li jikkawża l-marda liċ-ċelloli tagħna. Filwaqt li dan il-kodiċi ma jistax imarradna, huwa kapaċi jqanqal rispons immunitarju, li jgħallem is-sistema tagħna kif tiġġieled il-marda.
Il-vaċċini minn vettur virali kapaċi jikkawżaw rispons immunitarju qawwi, jiġifieri jistgħu joffru livell għoli ta’ protezzjoni kontra infezzjoni jew mard sever.
Vaċċini inattivati fihom viruses li ġew inattivati (maqtula) f’laboratorju bl-użu ta’ sħana jew kimiċi.
Il-viruses inattivati ma jistgħux jirriproduċu ruħhom jew jikkawżaw mard iżda xorta jistgħu jipproduċu rispons immunitarju fil-ġisem. Meta persuna tirċievi vaċċin inattivat, is-sistema immunitarja tagħha tidentifika l-viruses inattivi bħala barranin. Dan jgħallem lill-ġisem biex jipproduċi antikorpi biex jiġġieled il-viruses.
Vaċċini ħajjin attenwati fihom viruses jew batterji ħajjin li ddgħajfu billi jibdlu d-DNA tagħhom jew billi jintgħażlu viruses jew batterji l-aktar dgħajfa biex jiġu inklużi fil-vaċċin.
Viruses u batterji mdgħajfa f’vaċċini ħajjin attenwati ma jistgħux jikkawżaw mard iżda xorta jistgħu jipproduċu rispons immunitarju fil-ġisem. Meta persuna tirċievi vaċċin attenwat ħaj, is-sistema immunitarja tidentifika l-batterji jew il-viruses imdgħajfa bħala barranin. Dan iġiegħel lill-ġisem jipproduċi antikorpi biex jiġġieled il-batterji jew il-viruses.
Vaċċini ħajjin attenwati jipproduċu rispons immunitarju qawwi li jista’ jdum żmien twil. Dan ifisser li jista’ jkun hemm bżonn ta’ inqas dożi milli għal tipi oħra ta’ vaċċini.
Vaċċini ħajjin u komuni attenwati huma l-vaċċin kontra l-ħosba, il-gattone u r-Rubella (MMR) u l-vaċċin kontra l-ġidri r-riħ.
L-ewwel vaċċin li qatt ġie żviluppat kien vaċċin ħaj attenwat. Dan kien vaċċin kontra l-ġidri, żviluppat fl-1798. It-teknoloġija tal-vaċċini ħajjin attenwati għadha tintuża llum f’vaċċini moderni bħal dawk għall-ħosba, il-ġidri r-riħ u d-deni isfar.
Il-vaċċini tossojdi fihom tossini li ġew inattivati u għalhekk ma għadhomx tossiċi.
It-tossini huma sustanzi kimiċi prodotti mill-batterji u li jistgħu jikkawżaw xi mard, bħat-tetnu u d-difterite.
It-tossojdi jsiru fil-laboratorju billi jiġu diżattivati t-tossini li jikkawżaw il-mard, bl-użu ta’ sustanzi kimiċi jew sħana.
It-tossini inattivati f’vaċċini tossojdi ma jistgħux jikkawżaw mard iżda xorta jistgħu jipproduċu rispons immunitarju fil-ġisem. Meta persuna tirċievi vaċċin tossojde, is-sistema immunitarja timmira t-tossini diżattivati u titgħallem kif tinnewtralizzahom. Dan jgħallem lill-ġisem kif jiddiżattiva t-tossini u jipprevjeni l-marda fil-futur.
Il-vaċċini tossojdi jgħallmu lill-ġisem biex jiġġieled it-tossini prodotti mill-batterji aktar milli jiġġieled il-batterji nfushom.
Il-vaċċini tossojdi spiss jinkludu aġġuvant biex ir-rispons isir aktar b’saħħtu.
Vaċċini tossojdi komuni huma dawk użati kontra t-tetnu u d-difterite.
Approvazzjoni tal-vaċċini fl-UE
Skopri kif l-awtoritajiet fl-Ewropa jittestjaw biex jiżguraw li l-vaċċini jkunu sikuri u effettivi qabel ma jiġu approvati għall-użu.
Il-benefiċċji tat-tilqim
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COVID-19 medicines
European Medicines Agency - Safety of COVID-19 vaccines