Calculate total score and categorize it based on input

I'm trying to create an application for the SLE disease scoring system, in which each symptom is represented by a different number, 

The total of symptom scores will be divided into a range of scores to determine disease activity.

Here is the code that I'm trying to write, but I haven't been able to figure out what the problem is that is keeping this program from running.

ui <- fluidPage(
    checkboxGroupInput("variable", "Variables to show:",
                       c("Neurological disorder" = "neu",
                         "Kidney disorder" = "gin",
                         "Vasculitis" = "vas",
                         "Haemolysis/ Thrombositopenia" = "hem",
                         "Myositis" = "mio",
                         "Artritis" = "art",
                         "Mucocutaneous disorder" = "muc",
                         "Serositis" = "ser",
                         "Fever/ Fatique" = "fev",
                         "Leukopenia/ Lhymphopenia" = "leu"
                         )),
    textOutput("data")
)

server <- function(input, output, session) {

       
    output$data <- reactive({
        input$neu == 8
        input$gin == 6
        input$vas == 4
        input$hem == 3
        input$mio == 3
        input$art == 2
        input$mio == 2
        input$ser == 2
        input$fev == 1
        input$leu == 1
        
    
        total <- input$neu + input$gin + input$vas + input$hem + input$mio +  
            input$art + input$mio + input$ser + input$fev + input$fev + input$leu
        
        if (total <= 2) {"Mild disease activity"}
        else if (total > 2 && < 5) {"Moderate disease activity"}
        else if (total > 5) {"Severe disease activity"}
})

shinyApp(ui, server)

Thank you for your help