本文是一篇優秀的essay代寫范文，題目為Why don't we have a vaccine to prevent AIDS?文章內容主要討論了為什么我們沒有艾滋病的疫苗。獲得性免疫缺陷綜合癥或通常簡稱為AIDS，是當今人類面臨的對我們健康的最大威脅之一。它是由人類免疫缺陷病毒或HIV引起的。換句話說，艾滋病是艾滋病病毒感染的晚期。自1982年春季在美國報道第一例艾滋病以來，已有3500萬人感染了艾滋病毒，約有2500萬人由于艾滋病并發癥而喪生。
Why don't we have a vaccine to prevent AIDS?
Acquired Immunodeficiency Syndrome or commonly abbreviated as AIDS, is one of the biggest threats to our health that we human beings are facing nowadays. It is caused by the Human Immunodeficiency Virus or HIV. In another word, AIDS is the late stage of HIV disease. Since the first AIDS was reported in the United States in the spring of 1982, more than 35 million people have contracted the HIV, and about 25 million people lost their life because of the complications caused by AIDS. HIV is fatal in that it attacks out bodies’ immune systems, which produce white blood cells and antibodies responsible for attacking viruses and bacteria. It is as if that the HIVs are spies that ambushed in the barracks of the forts and disable all the soldiers. Without soldiers (immune system), the forts (out bodies) are much easier to be conquered by other ailments, like flues.
獲得性免疫缺陷綜合癥（Acquired Immunodeficiency Syndrome，簡稱AIDS）是當今人類面臨的最大健康威脅之一。它是由人類免疫缺陷病毒或艾滋病毒引起的。換言之，艾滋病是HIV疾病的晚期。自1982年春美國報告第一例艾滋病以來，已有3500多萬人感染艾滋病毒，約2500萬人因艾滋病并發癥而喪生。艾滋病毒是致命的，因為它攻擊人體的免疫系統，免疫系統產生白細胞和抗體，負責攻擊病毒和細菌。兵營里所有的士兵都被伏擊了。如果沒有士兵（免疫系統），堡壘（外軀殼）更容易被其他疾病征服，比如煙道。
Some people may ask that since we have already defeated those seemingly invincible diseases such as measles, smallpox and mumps by using vaccine, is there a vaccine for HIV? Although scientists have been struggling for years trying to create vaccines for the AIDS, unfortunately, completely competent vaccine has not been invented yet. That is because HIV is a very complex, highly changeable virus, which makes speedy development of a successful preventive HIV vaccine extremely difficult.
HIV is spread when infected blood, semen, vaginal fluids, or breast milk gets into another person. Thus, there are several ways for the HIV to transmit: sexual transmission, blood transmission and vertical transmission. The current worldwide expansion of the AIDS epidemic is primarily driven by the sexual transmission, either heterosexual or homosexual. Also, transmission of HIV can occur following transfusion of blood product derived from an infected person’s blood. The perinatal transmission of HIV virtually account for all new HIV infections in children. As long as we know these means by which HIV spread, we can take measures to avoid AIDS by these following ways. Firstly, practice safe sex. Remember to use a condom with spermicide for anal, vaginal or oral penetration. Secondly, avoid sharing needles with other person. Thirdly, use medial latex gloves if we will be coming into contact with another person’s blood, urine, feces or semen. Indeed, HIV is fatal, but as long as we follow the rule listed above, there is no chance for us to contract the HIV. Meanwhile, we should also know that the HIV is not transmitted through daily hugging, kissing, message, shaking hands, insect bites and sharing showers or toilets with someone else with HIV.
As what I mentioned above, there is no cure for AIDS currently, but it may be treated with number of different antiretroviral drugs, often in combination. Early treatment with retrovirals, as soon as a person tests positive for infection with HIV, has been shown in studies to reduce to the transmission of HIV. Drugs such as AZT, DDI, and 3TC, which are reverse transcriptase inhibitors, have proved effective in delaying the onset of symptoms in certain subsets of infected individuals. The addition of a protease inhibitor, such as saquinovir, amprenavir, and atazanavir has proved very effective, but the drug combination does not eliminate the virus from the body. Thus, the current treatments are aimed to make patients live longer, lower their risk of developing non-HIV-related illness and to reduce the chances to transmit HIV to others.
A good piece of news is that the Thai HIV vaccine efficacy trial, known as RV144, demonstrated that latest vaccine was safe and modestly effective in preventing HIV infection. Therefore, we have to be confident, believing that we will finally defeat the AIDS just as we defeat those so-called cureless diseases like plague or smallpox hundreds years ago!